tag:theconversation.com,2011:/nz/topics/mosquitoes-5472/articlesMosquitoes – The Conversation2024-03-19T12:23:24Ztag:theconversation.com,2011:article/2237062024-03-19T12:23:24Z2024-03-19T12:23:24ZFemale mosquitoes rely on one another to choose the best breeding sites − and with the arrival of spring, they’re already on the hunt<figure><img src="https://images.theconversation.com/files/582309/original/file-20240315-26-7bf0sq.jpg?ixlib=rb-1.1.0&rect=30%2C0%2C6789%2C4468&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">_Aedes aegypti_, found across much of the U.S., spread Zika, dengue, chikungunya and other viruses.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/aedes-aegypti-mosquito-pernilongo-with-white-spots-royalty-free-image/1282216815">Mailson Pignata/iStock via Getty Images</a></span></figcaption></figure><p><em>Aedes aegypti</em> mosquitoes, one of the <a href="https://www.cdc.gov/mosquitoes/mosquito-control/professionals/range.html">most common species in the U.S.</a>, love everything about humans. They love our <a href="http://dx.doi.org/10.1126/science.adi8213">body heat and odors</a>, which enable them to find us. They love to feed on our blood to make their eggs mature. They even love all the standing water that we create. Uncovered containers, old tires and junk piles collect water and are perfect for breeding. </p>
<p>And with the advent of warm weather across the southern U.S., <a href="https://www.mosquitomagnet.com/articles/mosquito-season">mosquito breeding season is already underway</a>.</p>
<p>Given all the options that <em>Aedes</em> females have in urban areas, how do these cosmopolitan mosquitoes find the perfect site to lay their eggs? Scientists previously thought this was a solitary act, but now research shows that female <em>Aedes aegypti</em> mosquitoes – the main vector in the U.S. for diseases such as <a href="https://theconversation.com/explainer-where-did-zika-virus-come-from-and-why-is-it-a-problem-in-brazil-53425">Zika, dengue, chikungunya</a> and other viruses – can rely on one another for good reviews of breeding sites. </p>
<p>Our <a href="https://www.degennarolab.org/">Laboratory of Tropical Genetics</a> at Florida International University discovered a new behavior in which these mosquitoes <a href="https://doi.org/10.1038/s42003-024-05830-5">work together to find suitable egg-laying sites</a>. These findings, recently published in Communications Biology, show that mosquitoes regulate their own population density at breeding sites – an insight that could inform future mosquito control efforts.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/581972/original/file-20240314-30-jxgzpm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A half-dozen mosquitoes spread along the inside of a container." src="https://images.theconversation.com/files/581972/original/file-20240314-30-jxgzpm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/581972/original/file-20240314-30-jxgzpm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=750&fit=crop&dpr=1 600w, https://images.theconversation.com/files/581972/original/file-20240314-30-jxgzpm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=750&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/581972/original/file-20240314-30-jxgzpm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=750&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/581972/original/file-20240314-30-jxgzpm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=943&fit=crop&dpr=1 754w, https://images.theconversation.com/files/581972/original/file-20240314-30-jxgzpm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=943&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/581972/original/file-20240314-30-jxgzpm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=943&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"><em>Aedes aegypti</em> female mosquitoes laying their eggs in a laboratory breeding container.</span>
<span class="attribution"><span class="source">Kaylee Marrero</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Where and why female mosquitoes cluster</h2>
<p>Scientists know that female mosquitoes can be picky when it comes to where they lay their eggs. <em>Aedes aegypti</em> look for human-made breeding sites with relatively clean water, such as birdbaths, tires or even water-filled trash. But given two equal choices, you might expect them to spread evenly between the two. </p>
<p>On the contrary, when we released females in a two-choice test where both breeding site options were equivalent, we repeatedly found more mosquitoes in one chamber than in the other. Furthermore, this occurred irrespective of where the preferred chamber was positioned, whether the mosquitoes could touch water or whether mosquito eggs were already present at the breeding sites. </p>
<p>Female mosquitoes clearly were following one another in small groups to one breeding site rather than another – a newly discovered behavior in <em>Aedes aegypti</em> that we call aggregation. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/581971/original/file-20240314-26-70qvqk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Two ramekins, one with a few black spots in it, the other with many spots." src="https://images.theconversation.com/files/581971/original/file-20240314-26-70qvqk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/581971/original/file-20240314-26-70qvqk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=319&fit=crop&dpr=1 600w, https://images.theconversation.com/files/581971/original/file-20240314-26-70qvqk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=319&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/581971/original/file-20240314-26-70qvqk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=319&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/581971/original/file-20240314-26-70qvqk.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=401&fit=crop&dpr=1 754w, https://images.theconversation.com/files/581971/original/file-20240314-26-70qvqk.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=401&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/581971/original/file-20240314-26-70qvqk.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=401&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The black spots in the container on the right indicate that <em>Aedes aegypti</em> females have chosen it as a place to lay their eggs over the identical site on the left.</span>
<span class="attribution"><span class="source">Kaylee Marrero</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>The insects evidently preferred not to lay their eggs alone. When we tested 30 mosquitoes in our trials, they chose one site over another by a 2-to-1 margin. However, this changed as the test population increased beyond 30 mosquitoes. When we tested 60 or 90 females, the aggregation disappeared.</p>
<p>This tells us that females can regulate their own density at breeding sites – a response that likely is a mechanism to limit larval competition.</p>
<h2>Mosquitoes are smelling each other</h2>
<p>Mosquitoes largely sense the world through smell, using three families of <a href="https://www.britannica.com/science/olfactory-receptor">olfactory receptors</a>. These receptors detect odors when females are choosing where to lay eggs. But how do females sense each other to regulate their densities at breeding sites? </p>
<p>We explored this question by first placing 15 mosquitoes at one of our two test breeding sites. Other females seeking a place to lay preferred the unoccupied site over the one that was already occupied, even though we had already observed that the mosquitoes preferred not to lay their eggs alone. Something was directing them away from the occupied breeding site; we speculated that it might be carbon dioxide, which is an important cue for mosquitoes in all stages of their life cycle. </p>
<p>When female mosquitoes are looking for a blood meal, they fly toward the odor of CO₂, which all vertebrate animals <a href="https://theconversation.com/why-are-some-people-mosquito-magnets-and-others-unbothered-a-medical-entomologist-points-to-metabolism-body-odor-and-mindset-187957">exhale and release through their skin</a>. After feeding, they fly away from it, likely to avoid the risk of being killed by the host. </p>
<p>Mosquitoes also emit CO₂, and normally other mosquitoes can smell it, thanks to a receptor component called Gr3 in their olfactory organs. But when we released mutant females that lacked a functional Gr3 receptor to seek a place to lay eggs in our two-site test, we found that these insects, which could not detect CO₂, were willing to lay their eggs at preoccupied breeding sites. This suggested that normal mosquitoes might be avoiding the preoccupied laying site because they smelled CO₂ emitted by mosquitoes that were already there.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/EUrOcquy8IU?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Female mosquitoes lay eggs on or near still bodies of water.</span></figcaption>
</figure>
<p>To confirm this, we offered two unoccupied breeding sites to females seeking a place to lay. However, we increased CO₂ levels around one of the sites to between 600 and 750 parts per million, compared with the normal level of about 450 to 500 ppm at the other site. We found that <em>Aedes aegypti</em> females avoided the unoccupied sites with elevated CO₂. This behavior appears designed to keep occupied breeding sites from becoming too crowded. </p>
<p>Overall, we found that two families of receptors play a role in the interactions between <em>Aedes aegypti</em> females when they seek breeding sites. Odorant receptors detect an unknown odor, which draws females toward a site; gustatory receptors detect CO₂, which deters females from breeding sites when the carbon dioxide level is high. The balance between these attractive and repellent odors will ultimately determine whether a female chooses or avoids a particular site. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/582583/original/file-20240318-20-i9yyck.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Graphic showing common mosquito breeding sites around home, including gutters and pet dishes." src="https://images.theconversation.com/files/582583/original/file-20240318-20-i9yyck.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/582583/original/file-20240318-20-i9yyck.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/582583/original/file-20240318-20-i9yyck.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/582583/original/file-20240318-20-i9yyck.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/582583/original/file-20240318-20-i9yyck.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/582583/original/file-20240318-20-i9yyck.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/582583/original/file-20240318-20-i9yyck.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Mosquitoes breed in many wet spots, large and small.</span>
<span class="attribution"><a class="source" href="https://www.cabq.gov/environmentalhealth/urban-biology/mosquitoes">City of Albuquerque</a>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Implications for mosquito control</h2>
<p>Suppressing mosquito populations in urban areas using <a href="https://www.cdc.gov/mosquitoes/mosquito-control/community/larvicides.html">biolarvicides</a> – pesticides made from live bacteria that are toxic to mosquito larvae – is a primary control strategy to limit the spread of deadly diseases such as West Nile virus and Zika virus. This is especially true for <em>Aedes aegypti</em>, which is the most common urban mosquito species that reproduces in artificial breeding sites that humans create. Other control tactics, such as <a href="https://undark.org/2019/10/25/when-residents-say-no-to-aerial-mosquito-spraying/">spraying pesticides over large areas</a>, target beneficial insects as well as mosquitoes and can be controversial. </p>
<p>Knowing that female <em>Aedes aegypti</em> use social cues to pick the best breeding grounds for their young and will move on from a breeding site when it becomes too crowded could lead to new control measures. Interrupting the female mosquito reproductive cycle would reduce the spread of mosquitoes and the spread of diseases that these insects carry.</p><img src="https://counter.theconversation.com/content/223706/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kaylee Marrero receives funding from the National Institutes of Health.</span></em></p><p class="fine-print"><em><span>Andre Luis Costa-da-Silva receives funding from the Centers for Disease Control and Prevention, the Southeastern Center of Excellence in Vector-borne Disease and the National Institutes of Health. Views expressed in this article are his own. </span></em></p><p class="fine-print"><em><span>Matthew DeGennaro receives funding from the Centers for Disease Control and Prevention (CDC), the Southeastern Center of Excellence in Vector-borne Disease and the National Institutes of Health. Views expressed in this article are his own.</span></em></p>Female mosquitoes don’t want to lay their eggs alone, but they don’t want sites that are too crowded either. Understanding what guides their choice could inform new control strategies.Kaylee Marrero, Ph.D. Student and Transdisiplinary Biomolecular and Biomedical Sciences Fellow, Florida International UniversityAndre Luis da Costa da Silva, Research Assistant Professor of Biological Sciences, Florida International UniversityMatthew DeGennaro, Associate Professor of Biological Sciences, Florida International UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2217382024-01-23T23:50:48Z2024-01-23T23:50:48ZMosquitoes can spread the flesh-eating Buruli ulcer. Here’s how you can protect yourself<figure><img src="https://images.theconversation.com/files/570835/original/file-20240123-15-oolw3x.JPG?ixlib=rb-1.1.0&rect=10%2C395%2C6939%2C2886&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">A/Prof Cameron Webb (NSW Health Pathology)</span></span></figcaption></figure><p>Each year, more and more Victorians become sick with a flesh-eating bacteria known as Buruli ulcer. <a href="https://www.premier.vic.gov.au/take-precautions-against-buruli-ulcer-summer">Last year</a>, 363 people presented with the infection, the highest number since 2004. </p>
<p>But it has been unclear exactly how it spreads, until now. <a href="https://www.nature.com/articles/s41564-023-01553-1">New research</a> shows mosquitoes are infected from biting possums that carry the bacteria. Mozzies spread it to humans through their bite.</p>
<h2>What is Buruli ulcer?</h2>
<p><a href="https://www.betterhealth.vic.gov.au/health/healthyliving/Buruli-ulcer">Buruli ulcer</a>, also known as Bairnsdale ulcer, is a skin infection caused by the bacterium <em>Mycobacterium ulcerans</em>.</p>
<p>It starts off like a small mosquito bite and over many months, slowly develops into an ulcer, with extensive destruction of the underlying tissue.</p>
<p>While often painless initially, the infection can become very serious. If left untreated, the ulcer can continue to enlarge. This is where it gets its “flesh-eating” name. </p>
<p>Thankfully, it’s treatable. A six to eight week course of specific antibiotics is an effective treatment, sometimes supported with surgery to remove the infected tissue.</p>
<h2>Where can you catch it?</h2>
<p>The <a href="https://www.who.int/news-room/fact-sheets/detail/buruli-ulcer-(mycobacterium-ulcerans-infection)">World Health Organization</a> considers Buruli ulcer a neglected tropical skin disease. Cases have been reported across 33 countries, primarily in west and central Africa. </p>
<p>However, since the early 2000s, Buruli ulcer has also been increasingly recorded in coastal Victoria, including suburbs <a href="https://www.theguardian.com/australia-news/2024/jan/18/flesh-eating-buruli-ulcer-cases-victoria-warning-rise-mosquito">around Melbourne</a> and Geelong.</p>
<p>Scientists have long known <a href="https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0002666">Australian native possums</a> were partly responsible for its spread, and suspected <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3375796/">mosquitoes</a> also played a role in the increase in cases. <a href="https://www.nature.com/articles/s41564-023-01553-1">New research</a> confirms this.</p>
<h2>Our efforts to ‘beat Buruli’</h2>
<p>Confirming the role of insects in outbreaks of an infectious disease is <a href="https://www.health.vic.gov.au/infectious-diseases/beating-buruli-in-victoria">achieved</a> by building up corroborating, independent evidence. </p>
<p>In this <a href="https://www.nature.com/articles/s41564-023-01553-1">new research</a>, published in Nature Microbiology, the team (including co-authors Tim Stinear, Stacey Lynch and Peter Mee) conducted extensive surveys across a 350 km² area of Victoria. </p>
<p>We collected mosquitoes and analysed the specimens to determine whether they were carrying the pathogen, and links to infected possums and people. It was like <a href="https://theconversation.com/explainer-what-is-contact-tracing-and-how-does-it-help-limit-the-coronavirus-spread-134228">contact tracing</a> for mosquitoes.</p>
<figure class="align-left ">
<img alt="Dead mosquito specimen in museum collection" src="https://images.theconversation.com/files/570827/original/file-20240123-17-zkh06a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/570827/original/file-20240123-17-zkh06a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=900&fit=crop&dpr=1 600w, https://images.theconversation.com/files/570827/original/file-20240123-17-zkh06a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=900&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/570827/original/file-20240123-17-zkh06a.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=900&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/570827/original/file-20240123-17-zkh06a.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1131&fit=crop&dpr=1 754w, https://images.theconversation.com/files/570827/original/file-20240123-17-zkh06a.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1131&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/570827/original/file-20240123-17-zkh06a.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1131&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Aedes notoscriptus was the mosquito identified as carrying the bacteria that caused Buruli ulcer.</span>
<span class="attribution"><span class="source">Cameron Webb (NSW Health Pathology)</span></span>
</figcaption>
</figure>
<p>Molecular testing of the mosquito specimens showed that of the two most abundant mosquito species, only <em>Aedes notoscriptus</em> (a widespread species commonly known as the Australian backyard mosquito) was positive for <em>Mycobacterium ulcerans</em>. </p>
<p>We then used genomic tests to show the bacteria found on these mosquitoes matched the bacteria in possum poo and humans with Buruli ulcer.</p>
<p>We further analysed mosquito specimens that contained blood to show <em>Aedes notoscriptus</em> was feeding on both possums and humans.</p>
<p>To then link everything together, geospatial analysis revealed the areas where human Buruli ulcer cases occur overlap with areas where both mosquitoes and possums that harbour <em>Mycobacterium ulcerans</em> are active.</p>
<h2>Stop its spread by stopping mozzies breeding</h2>
<p>The mosquito in this study primarily responsible for the bacteria’s spread is <em>Aedes notoscriptus</em>, a mosquito that lays its eggs around water in containers in backyard habitats. </p>
<p>Controlling “backyard” mosquitoes is a critical part of reducing the risk of many global mosquito-borne disease, <a href="https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0003713">especially dengue</a> and now Buruli ulcer. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/its-warming-up-and-mozzies-are-coming-heres-how-to-mosquito-proof-your-backyard-212711">It's warming up and mozzies are coming. Here's how to mosquito-proof your backyard</a>
</strong>
</em>
</p>
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<p>You can reduce places where water collects after rainfall, such as potted plant saucers, blocked gutters and drains, unscreened rainwater tanks, and a wide range of plastic buckets and other containers. These should all be either <a href="https://theconversation.com/you-can-leave-water-out-for-wildlife-without-attracting-mosquitoes-if-you-take-a-few-precautions-128631">emptied at least weekly</a> or, better yet, thrown away or placed under cover.</p>
<figure class="align-center ">
<img alt="A watering can sitting in garden and filled with water" src="https://images.theconversation.com/files/570830/original/file-20240123-27-akrcy.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/570830/original/file-20240123-27-akrcy.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/570830/original/file-20240123-27-akrcy.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/570830/original/file-20240123-27-akrcy.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/570830/original/file-20240123-27-akrcy.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/570830/original/file-20240123-27-akrcy.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/570830/original/file-20240123-27-akrcy.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Mosquitoes can lay eggs in a wide range of water-filled items in the backyard.</span>
<span class="attribution"><span class="source">Cameron Webb (NSW Health Pathology)</span></span>
</figcaption>
</figure>
<p>There is a role for insecticides too. While residual insecticides applied to surfaces around the house and garden will reduce mosquito populations, <a href="https://theconversation.com/the-battle-against-bugs-its-time-to-end-chemical-warfare-111629">they can also impact</a> other, beneficial, insects. Judicious use of such sprays is recommended. But there are <a href="https://onlinelibrary.wiley.com/doi/10.1111/j.1440-6055.2008.00642.x">ecological safe insecticides</a> that can be applied to water-filled containers (such as ornamental ponds, fountains, stormwater pits and so on).</p>
<p>Recent research also indicates new mosquito-control approaches that use <a href="https://academic.oup.com/jme/article/60/5/1061/7236697">mosquitoes themselves to spread insecticides</a> may soon be available.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/stickers-and-wristbands-arent-a-reliable-way-to-prevent-mosquito-bites-heres-why-220284">Stickers and wristbands aren't a reliable way to prevent mosquito bites. Here's why</a>
</strong>
</em>
</p>
<hr>
<h2>How to protect yourself from bites</h2>
<p>The first line of defence will remain personal protection measures against mosquito bites.</p>
<p>Covering up with loose fitted long sleeved shirts, long pants, and covered shoes will provide physical protection from mosquitoes.</p>
<p>Applying topical insect repellent to all exposed areas of skin has been proven to <a href="https://www.jaad.org/article/S0190-9622(18)32824-X/fulltext">provide safe and effective protection</a> from mosquito bites. Repellents should <a href="https://www.phrp.com.au/issues/december-2016-volume-26-issue-5/a-review-of-recommendations-on-the-safe-and-effective-use-of-topical-mosquito-repellents/">include</a> diethytolumide (DEET), <a href="https://www.phrp.com.au/issues/december-2016-volume-26-issue-5/a-review-of-recommendations-on-the-safe-and-effective-use-of-topical-mosquito-repellents/">picaridin</a> or oil of lemon eucalyptus.</p>
<p>While the rise in Buruli ulcer is a significant health concern, <a href="https://theconversation.com/how-can-the-bite-of-a-backyard-mozzie-in-australia-make-you-sick-171601">so too are many other mosquito-borne diseases</a>. The steps to avoid mosquito bites and exposure to <em>Mycobacteriam ulcerans</em> will also protect against viruses such as Ross River, Barmah Forest, Japanese encephalitis, and Murray Valley encephalitis.</p>
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Read more:
<a href="https://theconversation.com/how-can-the-bite-of-a-backyard-mozzie-in-australia-make-you-sick-171601">How can the bite of a backyard mozzie in Australia make you sick?</a>
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<img src="https://counter.theconversation.com/content/221738/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Cameron Webb and the Department of Medical Entomology, NSW Health Pathology, have been engaged by a wide range of insect repellent and insecticide manufacturers to provide testing of products and provide expert advice on mosquito biology. Cameron has also received funding from local, state and federal agencies to undertake research into mosquito-borne disease surveillance and management.</span></em></p><p class="fine-print"><em><span>Peter Mee receives funding from the National Health and Medical Research Council.</span></em></p><p class="fine-print"><em><span>Stacey Lynch receives funding from the National Health and Medical Research Council of Australia. The work on this subject was undertaken while employed in a former role at Agriculture Victoria.</span></em></p><p class="fine-print"><em><span>Tim Stinear receives funding from the National Health and Medical Research Council of Australia. </span></em></p>New research shows mosquitoes spread Buruli ulcer. So reducing mosquito populations and avoiding bites is critical.Cameron Webb, Clinical Associate Professor and Principal Hospital Scientist, University of SydneyPeter Mee, Adjunct Associate Lecturer, School of Applied Systems Biology, La Trobe UniversityStacey Lynch, Team Leader- Mammalian infection disease research, CSIROTim Stinear, Professor of Microbiology, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2202842024-01-18T01:00:18Z2024-01-18T01:00:18ZStickers and wristbands aren’t a reliable way to prevent mosquito bites. Here’s why<figure><img src="https://images.theconversation.com/files/569681/original/file-20240116-25-fkx3sy.jpg?ixlib=rb-1.1.0&rect=220%2C137%2C3918%2C3235&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/2-boys-standing-on-green-grass-near-lake-during-daytime-pwCJWny66aI">Meritt Thomas/Unsplash</a></span></figcaption></figure><p>Protecting yourself and family from mosquito bites can be challenging, especially in this hot and humid weather. Protests from young children and fears about topical insect repellents drive some to try alternatives such as wristbands, patches and stickers. </p>
<p>These products are sold online as well as in supermarkets, pharmacies and camping stores. They’re often marketed as providing “natural” protection from mosquitoes.</p>
<p>But unfortunately, they aren’t a reliable way to prevent mosquito bites. Here’s why – and what you can try instead. </p>
<h2>Why is preventing mosquito bites important?</h2>
<p>Mosquitoes can <a href="https://theconversation.com/how-can-the-bite-of-a-backyard-mozzie-in-australia-make-you-sick-171601">spread pathogens that make us sick</a>. <a href="https://theconversation.com/japanese-encephalitis-virus-has-been-detected-in-australian-pigs-can-mozzies-now-spread-it-to-humans-178017">Japanese encephalitis</a> and <a href="https://theconversation.com/murray-valley-encephalitis-has-been-detected-in-mozzies-in-nsw-and-victoria-heres-what-you-need-to-know-197894">Murray Valley encephalitis</a> viruses can have potentially fatal outcomes. While <a href="https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1005070">Ross River</a> virus won’t kill you, it can cause potentially debilitating illnesses. </p>
<p>Health authorities <a href="https://www.health.nsw.gov.au/Infectious/mosquito-borne/Pages/default.aspx">recommend</a> preventing mosquito bites by: avoiding areas and times of the day when mosquitoes are most active; covering up with long sleeved shirts, long pants, and covered shoes; and applying a topical insect repellent (a cream, lotion, or spray).</p>
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Read more:
<a href="https://theconversation.com/will-japanese-encephalitis-return-this-summer-what-about-other-diseases-mosquitoes-spread-218441">Will Japanese encephalitis return this summer? What about other diseases mosquitoes spread?</a>
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<h2>I don’t want to put sticky and smelly repellents on my skin!</h2>
<p>While for many people, the “sting” of a <a href="https://www.sciencedirect.com/science/article/pii/S1326020023023567?via%3Dihub">biting mosquitoes is enough to prompt a dose of repellent</a>, others are <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10739303/">reluctant</a>. Some <a href="https://www.liebertpub.com/doi/10.1089/153036603322662156">are deterred</a> by the unpleasant feel or smell of insect repellents. Others believe topical repellents contain chemicals that are dangerous to our health.</p>
<p>However, many studies have shown that, when used as recommended, these products <a href="https://www.sciencedirect.com/science/article/abs/pii/S1080603215004342">are safe to use</a>. All products marketed as mosquito repellents in Australia must be registered by the <a href="https://www.apvma.gov.au/">Australian Pesticides and Veterinary Medicines Authority</a>; a process that provides recommendations for safe use. </p>
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Read more:
<a href="https://theconversation.com/feel-like-youre-a-mozzie-magnet-its-true-mosquitoes-prefer-to-bite-some-people-over-others-128788">Feel like you're a mozzie magnet? It's true – mosquitoes prefer to bite some people over others</a>
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<h2>How do topical repellents work?</h2>
<p>While there remains some uncertainty about how the <a href="https://www.jaad.org/article/S0190-9622(18)32824-X/fulltext">chemicals in topical insect repellents actually work</a>, they appear to either block the sensory organs of mosquitoes that drive them to bite, or overpower the smells of our skin that helps mosquitoes find us. </p>
<p>Diethytolumide (DEET) is a <a href="https://www.phrp.com.au/issues/december-2016-volume-26-issue-5/a-review-of-recommendations-on-the-safe-and-effective-use-of-topical-mosquito-repellents/">widely recommended ingredient</a> in topical repellents. Picaridin and oil of lemon eucalyptus <a href="https://www.phrp.com.au/issues/december-2016-volume-26-issue-5/a-review-of-recommendations-on-the-safe-and-effective-use-of-topical-mosquito-repellents/">are also used</a> and have been shown to be effective and safe.</p>
<h2>How do other products work?</h2>
<p>“Physical” insect-repelling products, such as wristbands, coils and candles, often contain a botanically derived chemical and are often marketed as being an alternative to DEET.</p>
<p>However, studies have shown that devices such as candles <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/j.1365-3156.2011.02781.x">containing citronella oil</a> provide lower mosquito-bite prevention than topical repellents.</p>
<p>A <a href="https://search.informit.org/doi/abs/10.3316/INFORMIT.227605874334644?casa_token=DEdfTcUX-F0AAAAA%3AwKeVbAzCxFZX2BZj2VvHBqI3Vjv1oKngFHgMteebxGtZVfN5bezrWRbNnBHyoyKViaEG_908OOwCAC4">laboratory study in 2011</a> found wristbands infused with peppermint oil failed to provide full protection from mosquito bites.</p>
<p>Even as topical repellent formulations applied to the skin, these botanically derived products have <a href="https://bioone.org/journals/Journal-of-the-American-Mosquito-Control-Association/volume-25/issue-3/09-0016.1/Are-Commercially-Available-Essential-Oils-from-Australian-Native-Plants-Repellent/10.2987/09-0016.1.short">lower mosquito bite protection</a> than recommended products such as those containing <a href="https://www.phrp.com.au/issues/december-2016-volume-26-issue-5/a-review-of-recommendations-on-the-safe-and-effective-use-of-topical-mosquito-repellents/">DEET, picaridin and oil of lemon eucalyptus</a>.</p>
<p>Wristbands infused with DEET have shown mixed results but may provide some <a href="https://link.springer.com/article/10.1007/s00436-009-1433-x">bite protection</a> or <a href="https://resjournals.onlinelibrary.wiley.com/doi/10.1111/j.1365-2915.1987.tb00331.x">bite reduction</a>. DEET-based wristbands or patches are not currently available in Australia.</p>
<p>There is also a range of mosquito repellent <a href="https://theconversation.com/are-mosquito-coils-good-or-bad-for-our-health-88548">coils, sticks, and other devices</a> that release insecticides (for example, pyrethroids). These chemicals are primarily designed to kill or “knock down” mosquitoes rather than to simply keep them from biting us.</p>
<h2>What about stickers and patches?</h2>
<p>Although insect repellent patches and stickers have been available for many years, there has been a sudden surge in their marketing through social media. But there are very few scientific studies testing their efficacy.</p>
<p>Our current understanding of the way insect repellents work would suggest these small stickers and patches offer little protection from mosquito bites.</p>
<p>At best, they may <a href="https://bioone.org/journals/Journal-of-the-American-Mosquito-Control-Association/volume-22/issue-1/8756-971X(2006)22%5B158:FEONMS%5D2.0.CO;2/FIELD-EVALUATION-OF-NEW-MOUNTAIN-SANDALWOOD-MOSQUITO-STICKSsup-supAND-NEW/10.2987/8756-971X(2006)22%5B158:FEONMS%5D2.0.CO;2.short">reduce some bites</a> in the way mosquito coils containing botanical products work. However, the passive release of chemicals from the patches and stickers is likely to be substantially lower than those from mosquito coils and <a href="https://academic.oup.com/jme/article-abstract/53/2/480/2459702?login=false">other devices actively releasing chemicals</a>.</p>
<p>One <a href="https://doi.org/10.1016/j.actatropica.2012.10.009">study in 2013</a> found a sticker infused with oil of lemon eucalyptus “did not provide significant protection to volunteers”.</p>
<p><a href="https://theconversation.com/mozzie-repellent-clothing-might-stop-some-bites-but-youll-still-need-a-cream-or-spray-107266">Clothing impregnated with insecticides</a>, such as permethrin, will assist in reducing mosquito bites but topical insect repellents are still recommended for exposed areas of skin.</p>
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Read more:
<a href="https://theconversation.com/bzzz-slap-how-to-treat-insect-bites-home-remedies-included-148722">Bzzz, slap! How to treat insect bites (home remedies included)</a>
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<h2>Take care when using these products</h2>
<p>The idea you can apply a sticker or patch to your clothing to protect you from mosquito bites may sound appealing, but these devices provide a false sense of security. There is no evidence they are an equally effective alternative to the topical repellents recommended by health authorities around the world. It <a href="https://theconversation.com/curious-kids-when-we-get-bitten-by-a-mosquito-why-does-it-itch-so-much-93347">only takes one bite</a> from a mosquito to transmit the pathogens that result in serious disease.</p>
<p>It is also worth noting that there are some health warnings and recommendations for their use <a href="https://www.apvma.gov.au/">required by Australian Pesticides and Veterinary Medicines Authority</a>. Some of these products warn against application to the skin (recommending application to clothing only) and to keep products “out of reach of children”. This is a challenge if attached to young children’s clothing.</p>
<p>Similar warnings are associated with most other topical and non-topical mosquito repellents. Always check the labels of these products for safe use recommendations.</p>
<h2>Are there any other practical alternatives?</h2>
<p>Topical insect repellents are safe and effective. Most can be used on children from 12 months of age and pose no health risks. Make sure you apply the repellent as a thin even coat on all exposed areas of skin. </p>
<p>But you don’t need “tropical strength” repellents for short periods of time outdoors; a range of formulations with lower concentrations of repellent will work well for shorter trips outdoors. There are some repellents that don’t smell as strong (for example, children’s formulations, odourless formulations) or formulations that may be more pleasant to use (for example, pump pack sprays).</p>
<p>Finally, you can always cover up. Loose-fitting long-sleeved shirts, long pants, and covered shoes will provide a physical barrier between you and mosquitoes on the hunt for your or your family’s blood this summer.</p><img src="https://counter.theconversation.com/content/220284/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Cameron Webb and the Department of Medical Entomology, NSW Health Pathology, have been engaged by a wide range of insect repellent and insecticide manufacturers to provide testing of products and provide expert advice on mosquito biology. Cameron has also received funding from local, state and federal agencies to undertake research into mosquito-borne disease surveillance and management.</span></em></p>It’s hot and humid. With mosquitoes about, applying insect repellent creams, sprays and lotions may not feel good. But how do the alternatives stack up?Cameron Webb, Clinical Associate Professor and Principal Hospital Scientist, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2201682024-01-17T13:37:40Z2024-01-17T13:37:40ZDengue fever: the tropical disease spreading across Europe<figure><img src="https://images.theconversation.com/files/566586/original/file-20231214-23-8x6yy5.jpg?ixlib=rb-1.1.0&rect=73%2C73%2C5390%2C3563&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">The dengue virus is spread through bites from infected Aedes mosquitoes.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/es/image-photo/striped-mosquitoes-eating-blood-on-human-1510102085">Witsawat.S/Shutterstock</a></span></figcaption></figure><p>If you were looking for information on dengue fever and only had access to older textbooks, it would likely be found in the sections on tropical and subtropical diseases.</p>
<p>The disease is, indeed, spreading rapidly in warmer regions: Peru – which has mixed subtropical and tropical climates – has recently recorded some of <a href="https://www.unicef.org/peru/comunicados-prensa/mas-37-mil-ninas-ninos-adolescentes-enfermaron-de-dengue-primeros-meses-2023-recomendaciones-especialista">the highest numbers of the virus</a> (both cases and deaths) within memory. This has led to the declaration of a state of emergency in most of its regions, as cases continue to climb year after year.</p>
<h2>Record numbers of cases in 2023</h2>
<p>We are also seeing more and more new cases outside of Latin America. There have been increasing numbers of locally transmitted cases in the <a href="https://www.cdc.gov/dengue/statistics-maps/historic-data.html">USA</a>, <a href="https://www.eurosurveillance.org/content/10.2807/1560-7917.ES.2023.28.37.2300471">Italy</a> and <a href="https://www.santepubliquefrance.fr/en/autochthonous-dengue-in-mainland-france-2022-geographical-expansion-and-increase-in-incidence">France</a>, as well as the first recorded cases in many years in <a href="https://www.sanidad.gob.es/profesionales/saludPublica/ccayes/alertasActual/docs/20230228_ERR_Dengue_autoctono.pdf">Spain</a>.</p>
<p>In 2022, there were <a href="https://www3.paho.org/data/index.php/es/temas/indicadores-dengue/boletin-anual-arbovirosis-2022.html">2.8 million registered cases of dengue</a> on the American continent alone. This was more than double the 1.2 million cases in 2021.</p>
<p>Although the majority of cases affect <a href="https://www.who.int/emergencies/disease-outbreak-news/item/2023-DON448">tropical and subtropical areas of America, Asia and Africa</a>, a significant increase has recently been observed in more temperate areas, such as Europe. This is especially true in the south of the continent, where the disease has been present since the 1970s.</p>
<p>According to statistics from the <a href="https://www.ecdc.europa.eu/en/dengue-monthly">European Centre for Disease Prevention and Control</a>, 71 locally transmitted cases of dengue were reported in 2022 in mainland EU countries. This is an increase of over 20% compared to 2021.</p>
<h2>Small bites, big consequences</h2>
<p><a href="https://www.who.int/news-room/fact-sheets/detail/dengue-and-severe-dengue">Dengue</a> is a disease caused by one of the four strains of dengue virus (DENV). It has been reported that all four strains can circulate together, and that they can cause the same set of symptoms. Special attention should be given to severe or haemorrhagic dengue, which is usually caused by exposure to one strain after previous exposure to another.</p>
<p>DENV is <a href="https://www.cdc.gov/dengue/transmission/index.html">transmitted</a> through bites from infected <em>Aedes</em> mosquitoes, primarily <em>Aedes aegypti</em>, but also to a lesser extent <em>Aedes albopictus</em>, also known as the Tiger Mosquito. These insects, which feed on human blood and transmit the virus through their saliva, are found in tropical and subtropical areas. However, in recent decades they have become more and more common in temperate areas.</p>
<p>The virus is not transmitted directly, but works in a cycle, passing from human to mosquito to human. When an infected female <em>Aedes</em> mosquito bites a person, it introduces DENV into their system and begins the cycle. The incubation period is usually between 3 and 10 days, although it can vary depending on external factors such as temperature.</p>
<p>Symptoms then begin to develop, usually fever, headaches, muscle aches, joint pain, nausea and vomiting. In severe cases, it can lead to haemorrhage, organ failure and death.</p>
<p><em>Aedes</em> mosquitoes breed in standing or stagnant water, such as water containers, unused swimming pools, old tyres, and so on. In the absence of vaccines and effective treatments, it is important to eliminate mosquito breeding sites to prevent the transmission of the disease. This can not only prevent the spread of dengue, but also the mosquito-borne viruses that cause Zika and chikungunya.</p>
<h2>The role of climate change and globalisation</h2>
<p>Climate change is one of the <a href="https://pubmed.ncbi.nlm.nih.gov/30884421/">driving forces behind the rise in dengue cases</a>, both in America and Europe. Increased temperatures and longer mosquito breeding seasons (due to warmer and longer summers) may help the spread of <em>Aedes aegypti</em>.</p>
<p>These mosquitoes are able to survive in temperatures above 10C, and thanks to global warming they are able expand their range to more temperate zones. Changes in rainfall patterns – caused by climate change – also increase the volume of standing water, providing an ideal breeding ground.</p>
<p>In addition, increased international travel and trade with areas where dengue fever is common, as well as the growth of cities, make the spread of the disease all the more likely.</p>
<h2>Will dengue become endemic in Europe?</h2>
<p>Against this backdrop, the possibility of dengue becoming endemic in Europe is a real possibility. Environmental conditions such as climate change and globalisation are making it easier for mosquitoes – and the diseases they carry – to spread. These are factors that cannot easily be brought under control, at least for the time being.</p>
<p>If dengue were to become endemic in Europe, it could have a significant impact on public health. For this reason, <a href="https://climate-adapt.eea.europa.eu/en/observatory/evidence/health-effects/vector-borne-diseases/dengue-factsheet">European health authorities are already working</a> to prevent its spread by addressing the factors that can currently be controlled. This includes monitoring cases, educating populations on how to prevent mosquito bites, and taking measures to control new mosquito populations as soon as their presence is detected, as has been happening on the Spanish island of <a href="https://www.ull.es/portal/noticias/2023/sanidad-activa-con-ayuda-de-la-ull-el-protocolo-ante-la-deteccion-de-un-mosquito-aedes-albopictus-en-santa-cruz-de-tenerife/">Tenerife</a>.</p><img src="https://counter.theconversation.com/content/220168/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Raimundo Seguí López-Peñalver no recibe salario, ni ejerce labores de consultoría, ni posee acciones, ni recibe financiación de ninguna compañía u organización que pueda obtener beneficio de este artículo, y ha declarado carecer de vínculos relevantes más allá del cargo académico citado.</span></em></p>Climate change is causing dengue-carrying mosquitoes to spread. Could the disease become endemic in Europe?Raimundo Seguí López-Peñalver, Profesor de Epidemiología en VIU, Universidad Internacional de ValenciaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2189752023-12-29T11:40:00Z2023-12-29T11:40:00ZThe secret world of puddles<figure><img src="https://images.theconversation.com/files/565473/original/file-20231213-16-omthqc.jpg?ixlib=rb-1.1.0&rect=0%2C209%2C4169%2C3093&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Puddles can be valuable wildlife havens.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/water-splash-shoes-mens-feet-hiking-1857225058">Maksim Safaniuk/Shutterstock</a></span></figcaption></figure><p>As the new year arrived in 2016, my home city of Newcastle upon Tyne was briefly the centre of <a href="https://www.theatlantic.com/entertainment/archive/2016/01/the-puddle/422955/">global attention</a> – for a puddle. The Drummond Puddle, as it was grandly known, was a watery hazard placed perfectly where converging footpaths funnelled a daily stream of victims to their doom. To the wonderment of the world, their fate was <a href="https://www.youtube.com/watch?v=uRXuE7PBdLI">livestreamed</a> over the internet to more than half a million viewers. </p>
<p>But puddles are not merely a source of delight for wicked-minded onlookers. We can all, surely, remember the joy of splashing in a puddle – a universal example of creative play and getting to know the environment.</p>
<p>And yet, the conservation value of these tiny sites is still largely unappreciated. For puddles can be valuable wildlife havens too.</p>
<p>One <a href="https://doi.org/10.1016/j.limno.2012.07.002">study</a> of the invertebrate inhabitants of puddles in the UK countryside found a majority of these sites had a high conservation value, primarily due to the rare, specialist animals they hosted. Puddles may be commonplace, but their wildlife need not be.</p>
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<figcaption><span class="caption">This 2016 Periscope video shows people trying to avoid stepping in Newcastle’s Drummond Puddle.</span></figcaption>
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<h2>Your own private pool</h2>
<p>The tiny, fragmented, ephemeral world of puddles creates the ideal habitat for some species. The isolation and brief life of many of these mini-ponds keeps long-lived, larger predators and competitors at bay, opening up opportunities for more “live fast, die young” life. </p>
<p>In the UK, the most famous examples are the <a href="https://insidedio.blog.gov.uk/2018/10/22/an-exclusive-tour-around-the-plain/">fairy shrimps</a> of puddles on Salisbury Plain in Wiltshire. Large areas of Salisbury Plain are given over to military training, and the churning tracks of tanks create many temporary pools that house these muddy lodgers.</p>
<p>The eggs of the <a href="https://www.britannica.com/animal/fairy-shrimp">fairy shrimp</a> are resistant to drought. They remain dormant, but viable, for many years and are spread by the wind or, in the case of Salisbury Plain, are carried in the mud spattered on military vehicles. </p>
<p>When rain fills a track in the dried mud, fairy shrimp eggs hatch almost immediately. The shrimps grow quickly to lay a new generation of eggs before their puddle dries.</p>
<figure class="align-center ">
<img alt="Frozen puddles in tank tracks on Salisbury Plain." src="https://images.theconversation.com/files/565471/original/file-20231213-15-a9b1jz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/565471/original/file-20231213-15-a9b1jz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=355&fit=crop&dpr=1 600w, https://images.theconversation.com/files/565471/original/file-20231213-15-a9b1jz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=355&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/565471/original/file-20231213-15-a9b1jz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=355&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/565471/original/file-20231213-15-a9b1jz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=446&fit=crop&dpr=1 754w, https://images.theconversation.com/files/565471/original/file-20231213-15-a9b1jz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=446&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/565471/original/file-20231213-15-a9b1jz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=446&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Frozen puddles in tank tracks on Salisbury Plain, Wiltshire.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/snow-covered-frozen-iced-puddle-off-1914696466">Martin Hibberd/Shutterstock</a></span>
</figcaption>
</figure>
<p>Other landscapes also harbour important puddles that we have helped to create. The Lizard Peninsula in Cornwall supports a network of trackways that date back to pre-historic times. Temporary pools have developed within these trackways, supporting rare specialist plants like the <a href="https://www.conservationevidence.com/reference/pdf/4018">pygmy rush</a>. </p>
<p>In the US, over the past decade, the rare <a href="https://www.britannica.com/animal/clam-shrimp">clam shrimp</a> has <a href="https://urbanhabitats.org/v02n01/biodiversitypatterns_pdf.pdf">been found</a> in puddles on the dirt surface of a gas pipeline road in New Jersey. The clam shrimp had only previously been identified in a handful of sites in the north-eastern US.</p>
<h2>Puddle problems</h2>
<p>Human activity may also be creating puddles in urban landscapes. The rapid urbanisation of Beijing has been <a href="https://www.sciencedirect.com/science/article/pii/S1878029616302298">linked</a> with increasing the numbers of puddles in the Chinese capital, largely by accident as sites are demolished ready for new developments. As soon as the new build is started, however, these ponds are buried and lost.</p>
<p>The wildlife of urban puddles on roads and pavements has received much less attention compared with other urban habitats, such as flowerbeds or small ponds. But <a href="https://doi.org/10.12911/22998993/111463">research</a> in urban areas of south-east Poland shows that single-celled algae such as <a href="https://www.britannica.com/science/diatom">diatoms</a> and <a href="https://www.britannica.com/science/desmid">desmids</a> thrive in these puddle environments. </p>
<p><a href="https://www.sciencedirect.com/science/article/pii/S2530064420300225?via%3Dihub">Studies</a> in Brazil have also credited deforestation in the Xingu basin with driving “lentification” – creating water bodies that include puddles. Puddles in these more tropical regions of the world support the ominous presence of <a href="https://www.britannica.com/animal/mosquito-insect">mosquito larvae</a>. </p>
<p>The same safety from predators provided by puddles that benefits fairy and clam shrimps is also important to mosquitoes. In one <a href="https://www.researchgate.net/publication/335091956_Assessment_of_Physico-Chemical_and_Ecological_Variables_in_Selected_Natural_Breeding_Sites_of_Mosquitoes_in_Ibadan_Oyo_State_Nigeria">study</a> in Nigeria, <a href="https://www.britannica.com/animal/Anopheles"><em>Anopheles</em> mosquito</a> larvae were found in a higher proportion of road puddles than in other small water bodies.</p>
<p>Birds often look to exploit ponds and puddles, looking for drowned worms after prolonged rain. But worms are <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1744-7410.2007.00117.x">not that easy</a> to drown (although it varies by species). So maybe the sorry, soggy specimens stuck in puddles are just unlucky, slowed down as they flounder in the water, becoming very obvious to birds with an eye for an easy meal.</p>
<p>Puddles are, however, not a positive substitute for the problems caused by urbanisation and habitat loss. In Poland, birds using road puddles for a wash <a href="https://www.tandfonline.com/doi/full/10.1080/24750263.2022.2101699">risk</a> being killed by traffic. </p>
<h2>Planet puddle</h2>
<p>While we might be most familiar with the puddles of pavements and streets, there are natural puddle habitats too – and these are very widespread all over the planet. Puddles on ice sheets and glaciers called <a href="https://zslpublications.onlinelibrary.wiley.com/doi/abs/10.1111/jzo.12832">cryoconite holes</a> are home to a cosmopolitan fauna of <a href="https://www.britannica.com/animal/Devils-worm">nematode worms</a>, mites and the famously tough <a href="https://www.theguardian.com/science/2021/mar/20/tardigrades-natures-great-survivors">tardigrades</a>. </p>
<p>Puddles also occur in deserts, often as tiny rock pools. By arranging sticky traps around these rock pools, researchers in South Africa showed how wind dispersal <a href="https://link.springer.com/article/10.1007/s10750-009-9929-z">helps their inhabitants travel</a>. As the rock pools dried, the traps caught wind-borne eggs blowing in the dust, carrying a mix of <a href="https://www.britannica.com/animal/water-flea">waterfleas</a>, <a href="https://onlinelibrary.wiley.com/doi/10.1111/zsc.12505#:%7E:text=Laevicaudatan%20branchiopods%2C%20also%20called%20%E2%80%98smooth%20clam%20shrimps%E2%80%99%20or,90%25%20of%20which%20belong%20to%20the%20genus%20Lynceus.">pea shrimps</a> and <a href="https://www.britannica.com/animal/mite">mites</a>.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/565472/original/file-20231213-25-qdygg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="An image of a tardigrade under a microscope." src="https://images.theconversation.com/files/565472/original/file-20231213-25-qdygg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/565472/original/file-20231213-25-qdygg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=341&fit=crop&dpr=1 600w, https://images.theconversation.com/files/565472/original/file-20231213-25-qdygg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=341&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/565472/original/file-20231213-25-qdygg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=341&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/565472/original/file-20231213-25-qdygg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=429&fit=crop&dpr=1 754w, https://images.theconversation.com/files/565472/original/file-20231213-25-qdygg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=429&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/565472/original/file-20231213-25-qdygg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=429&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Tardigrades are famed among biologists for their ability to survive conditions that would kill almost any other animal.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/tardigrade-water-bear-microscope-magnification-2111263538">Videologia/Shutterstock</a></span>
</figcaption>
</figure>
<p>Urban puddles might still be the toughest environment of all, compared with the puddles in these glacier and desert habitats. But in all cases, there is much more to puddles than meets the eye – not just tiny shrimps or marooned worms.</p>
<p>Some of the strange creatures they contain are much more conspicuous. Video coverage of the Drummond Pond in Newcastle in 2016 even captured some two-legged inhabitants that appeared to be large, mammalian and naked …</p>
<hr>
<figure class="align-right ">
<img alt="Imagine weekly climate newsletter" src="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=600&fit=crop&dpr=1 600w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=600&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=600&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=754&fit=crop&dpr=1 754w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=754&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/434988/original/file-20211201-21-13avx6y.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=754&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<p class="fine-print"><em><span>Mike Jeffries does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Puddles are an often-ignored but crucial habitat for rare and unusual wildlife.Mike Jeffries, Associate Professor, Ecology, Northumbria University, NewcastleLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2197232023-12-13T10:59:52Z2023-12-13T10:59:52ZClimate change risks triggering a spike in infectious disease outbreaks: three reasons why<p>Climate change is our planet’s most immediate existential threat, and will likely only worsen for the foreseeable future. </p>
<p>Among its numerous adverse effects on human health, there is strong evidence linking climate change to <a href="https://www.science.org/doi/10.1126/science.1239401">infectious disease</a> outbreaks. </p>
<p>A recent analysis revealed that of 375 infectious diseases affecting human beings, 218 <a href="https://www.nature.com/articles/s41558-022-01426-1">(58%)</a> can be aggravated by climatic hazards. </p>
<p>It is no longer a question of “if”, but “when” an epidemic will be triggered or amplified by climate events.</p>
<p>It’s vital that swift, decisive action is taken to mitigate the impending public health crisis worsened by climate change. </p>
<p>We are part of the <a href="https://climade.health/">Climate Amplified Diseases and Epidemics consortium</a> launched in early 2023. The consortium is made up of leading molecular biologists, epidemiologists, ecologists and evolutionary biologists. </p>
<p>We engaged with hundreds of scientists from around the world to compile a report, the <a href="https://climade.health/cop28-report">Climate Change and Epidemics 2023 Synthesis</a>, which was launched in Dubai at COP28.</p>
<p>The team members who led the compilation of the report are from the <a href="https://climade.health/wp-content/uploads/2023/11/CLIMADE_COP28Report.pdf">global south</a>.
This is important, as the global south is likely to suffer the largest health effects from climate change.</p>
<p>The report identified three main reasons why climate change may aggravate infectious diseases.</p>
<ul>
<li><p>Increases in temperature and changes in <a href="https://ugc.berkeley.edu/background-content/precipitation/">precipitation patterns</a> create conditions for disease vectors, such as mosquitoes, to flourish and expand their distribution ranges.</p></li>
<li><p>More frequent extreme climatic events such as floods can cause surges of infections, for example by contaminating drinking water with faecal matter.</p></li>
<li><p>Climate-driven migration by people and their livestock can trigger outbreaks of infectious diseases.</p></li>
</ul>
<h2>How are diseases linked to climate change?</h2>
<p>Rising temperatures may create environments conducive for the spread of certain types of pathogens and their vectors. </p>
<p>For example, rising temperatures may increase the breeding rate of disease <a href="https://e360.yale.edu/features/dengue-fever-climate-change">vectors</a>, such as mosquitoes, and the infectious agents they carry, and expand their distribution ranges to new areas. </p>
<p><a href="https://www.health.ny.gov/diseases/communicable/arboviral/fact_sheet.htm#:%7E:text=Arboviral%20disease%20is%20a%20general,such%20as%20mosquitoes%20and%20ticks">Arboviruses</a>, which are transmitted by mosquitoes or ticks,
<a href="https://www.who.int/news-room/fact-sheets/detail/chikungunya#:%7E:text=Chikungunya%20is%20a%20mosquito%2Dborne,meaning%20%E2%80%9Cto%20become%20contorted%E2%80%9D.">chikungunya</a> and <a href="https://www.who.int/news-room/fact-sheets/detail/dengue-and-severe-dengue#:%7E:text=Overview,body%20aches%2C%20nausea%20and%20rash.">dengue</a> now occur in South Asia, South America and Europe in previously unaffected areas.</p>
<p><a href="https://www.nicd.ac.za/diseases-a-z-index/west-nile-fever/">West Nile virus</a> infections can now be acquired <a href="https://www.mdpi.com/1999-4915/12/4/448">north of the Alps</a>. </p>
<p>The changing climate increases the risk for many types of <a href="https://iopscience.iop.org/article/10.1088/2752-5295/ac6e7d/pdf">extreme events</a> such as floods, storms and droughts.</p>
<p>Extreme weather conditions often trigger the displacement of humans and animals, and impair the provision of essential supplies, medical care and transport. </p>
<p>This is particularly true of waterborne pathogens such as cholera. The world is currently in the <a href="https://www.who.int/emergencies/disease-outbreak-news/item/2023-DON437">seventh cholera pandemic</a>. </p>
<p>In 2022 and 2023, following two severe tropical storms causing widespread flooding and destruction, <a href="https://www.who.int/emergencies/disease-outbreak-news/item/2022-DON435">Malawi</a> experienced the deadliest outbreak of cholera in the country’s history. </p>
<p><a href="https://iopscience.iop.org/article/10.1088/2752-5295/ac6e7d/pdf">Droughts</a> also cause infection-related problems. People and their livestock may be forced to use unsafe water sources with higher concentrations of contaminants including water-borne pathogens. Hepatitis E outbreaks occur under conditions of <a href="https://www.who.int/news-room/fact-sheets/detail/hepatitis-e">water stress</a>.</p>
<p>Lastly, climate change may lead to large-scale displacement and migration of people and animals. The ongoing <a href="https://alliancebioversityciat.org/stories/el-nino-here-what-it-and-what-can-we-do">El Niño phenomenon</a> will likely produce severe drought in some regions of the world, potentially spurring mass temporary and permanent migrations. </p>
<p>This can lead to more and closer interactions with wildlife, which increases the risk of spillover of pathogens, including <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8182890/">novel ones</a>. </p>
<h2>Looking after the vulnerable</h2>
<p>Developing countries are more at risk of climate disasters. They also have <a href="https://climade.health/wp-content/uploads/2023/11/CLIMADE_COP28Report.pdf">less adaptive capacity</a> and preparedness to respond, leaving them highly vulnerable. </p>
<p>We call on governments, academic institutions and health organisations to expand genomic surveillance capabilities for early detection and to monitor the spread of infectious diseases. </p>
<p>Vulnerable communities are <a href="https://unfccc.int/sites/default/files/resource/Considerations%20regarding%20vulnerable.pdf">disproportionately affected</a> by climate change. These populations should be prioritised by investing in resilient healthcare systems and disaster preparedness measures. </p>
<h2>Saying no to ‘climate doomism’</h2>
<p>Rather than falling for <a href="https://yaleclimateconnections.org/2022/05/on-climate-doomism-heart-mind-reasons-to-resist-it/">“climate doomism”</a>, which tends to paralyse rather than trigger action, we prefer to learn from what has been achieved during the COVID-19 pandemic.</p>
<p>These achievements include novel epidemiological and infection control tools, including self-testing or smartphone apps, <a href="https://www.nicd.ac.za/diseases-a-z-index/disease-index-covid-19/surveillance-reports/weekly-reports/wastewater-based-epidemiology-for-sars-cov-2-in-south-africa/">wastewater epidemiology</a> and <a href="https://www.cdc.gov/coronavirus/2019-ncov/variants/genomic-surveillance.html#:%7E:text=Genomic%20Sequencing%3A%20Scientists%20use%20a,changes%20may%20affect%20public%20health.">genomic sequencing</a> to track the evolution of the agents that cause the disease.</p>
<p>Substantial capacity consisting of skilled people and adequate facilities has been built in much of the global south. This shows what is possible when the world works together. </p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/qi72DGfodJM?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure><img src="https://counter.theconversation.com/content/219723/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Prof. Wolfgang Preiser receives funding from various scientific grant funders, directly and indirectly, incl. South African NRF, PRF, NHLS-RT and more. He is affiliated with the University of Stellenbosch and South African National Health Laboratory Service (NHLS).</span></em></p><p class="fine-print"><em><span>Tulio de Oliveira receives funding from the South African Medical Council, the Rockefeller Foundation, the National Insitute of Health (NIH), the European Commission and other charities and government funding agencies. He is affiliated with the Centre for Epidemic Response and Innovation (CERI), Stellenbosch University, South Africa and the Genomics Surveillance Unit (GSU), Wellcome Sanger Institute, U.K.</span></em></p><p class="fine-print"><em><span>Cheryl Baxter, Houriiyah Tegally, and Monika Moir do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Heat, floods and droughts create conditions for pathogens and their vectors.Wolfgang Preiser, Head: Division of Medical Virology, Stellenbosch UniversityCheryl Baxter, Head Scientific Research Support, Stellenbosch UniversityHouriiyah Tegally, Senior Data Analyst, Head of Data Science at Centre for Epidemic Response and Innovation (CERI), Stellenbosch UniversityMonika Moir, Postdoctoral Researcher of Pathogen Genomics, Stellenbosch UniversityTulio de Oliveira, Director: KRISP - KwaZulu-Natal Research and Innovation Sequencing Platform, University of KwaZulu-NatalLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2184412023-12-04T19:13:29Z2023-12-04T19:13:29ZWill Japanese encephalitis return this summer? What about other diseases mosquitoes spread?<figure><img src="https://images.theconversation.com/files/562569/original/file-20231129-21-8z7c8x.jpg?ixlib=rb-1.1.0&rect=49%2C518%2C5499%2C2898&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/asian-woman-travel-camping-alone-natural-2122867583">Shutterstock</a></span></figcaption></figure><p>The last two summers have been swarming with mosquitoes thanks to near constant rain and flooding brought on by La Niña. </p>
<p>With <a href="https://www.sydney.edu.au/study/student-life/student-news/2023/11/20/the-bureau-of-meteorology-has-predicted-an-el-nino-this-summer-what-you-need-to-know.html">the return of El Niño</a>, and a hot, dry summer in store, what’s the outlook for Japanese encephalitis and other mosquito-borne diseases?</p>
<h2>First, let’s look back at the last two summers</h2>
<p>The boom in mosquitoes over the last two springs and summers didn’t just bring an <a href="https://theconversation.com/mozzies-are-everywhere-right-now-including-giant-ones-and-those-that-make-us-sick-heres-what-you-need-to-know-194517">increased annoyance of buzzing and bites</a> but also outbreaks of potentially fatal mosquito-borne disease.</p>
<p>The first outbreak of Japanese encephalitis virus was first detected in <a href="https://www.science.org/content/article/how-rains-pigs-and-waterbirds-fueled-shocking-disease-outbreak-australia">southern regions of mainland Australia</a> in February 2022.</p>
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Read more:
<a href="https://theconversation.com/murray-valley-encephalitis-has-been-detected-in-mozzies-in-nsw-and-victoria-heres-what-you-need-to-know-197894">Murray Valley encephalitis has been detected in mozzies in NSW and Victoria. Here's what you need to know</a>
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<p>This was followed by the return of <a href="https://theconversation.com/murray-valley-encephalitis-has-been-detected-in-mozzies-in-nsw-and-victoria-heres-what-you-need-to-know-197894">Murray Valley encephalitis</a> in early 2023, which turned out to be the biggest outbreak in the southern states <a href="https://pubmed.ncbi.nlm.nih.gov/37860808/">since 1974</a>.</p>
<p>These outbreaks were the result of more than just more mosquitoes. Floodwaters provided <a href="https://www.abc.net.au/news/2023-02-11/record-flooding-in-nsw-triggeres-bird-breeding-bonanza-/101812042">ideal breeding conditions</a> for waterbirds, the key “reservoirs” of these viruses. </p>
<p>Mosquitoes pick up the infection after feeding on the birds and then subsequently <a href="https://theconversation.com/curious-kids-when-we-get-bitten-by-a-mosquito-why-does-it-itch-so-much-93347">spread the viruses</a> to people when they bite.</p>
<h2>What’s different about Japanese encephalitis?</h2>
<p>Outbreaks of Japanese encephalitis virus in temperate regions of Australia in 2022 came as a surprise. There had <a href="https://www.mdpi.com/2414-6366/4/1/38/htm">been activity</a> in northern Australia and the Torres Strait, but it was generally <a href="https://theconversation.com/what-is-japanese-encephalitis-virus-and-how-can-i-avoid-it-when-i-travel-106775">only considered</a> a risk to overseas travellers.</p>
<p>In India, Southeast Asia, and the Western Pacific, Japanese encephalitis is <a href="https://www.who.int/news-room/fact-sheets/detail/japanese-encephalitis">considered</a> one of the most dangerous mosquito-borne diseases, with tens of thousands of cases of severe infection each year. </p>
<p>While the majority of people infected suffer no or very mild symptoms, some will <a href="https://www.health.gov.au/diseases/japanese-encephalitis">experience</a> neck stiffness, fever, headache and, in the most severe cases, permanent neurological complications or death.</p>
<p>However, a vaccine is available that can significantly limit serious illness. </p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/what-is-japanese-encephalitis-virus-and-how-can-i-avoid-it-when-i-travel-106775">What is Japanese encephalitis virus and how can I avoid it when I travel?</a>
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</p>
<hr>
<p>The <a href="https://theconversation.com/japanese-encephalitis-virus-has-been-detected-in-australian-pigs-can-mozzies-now-spread-it-to-humans-178017">discovery</a> of Japanese encephalitis virus in Australia’s southern states triggered a <a href="https://www.health.gov.au/news/statement-on-the-end-of-japanese-encephalitis-virus-emergency-response">declaration of</a> a “communicable disease incident of national significance”. This was in place from March 2022 through June 2023. A total of 45 people were infected, seven of whom sadly died. </p>
<p>It wasn’t just people who were at risk. The impact on commercial piggeries, which farm pigs for pork production, was <a href="https://www.porkbusiness.com/news/industry/australia-faces-pork-supply-shortages-due-japanese-encephalitis-production-losses">devastating</a> and required urgent strategies to <a href="https://www.farmbiosecurity.com.au/livestock/pigs/controlling-mosquitoes-around-piggeries/">control mosquitoes</a>.</p>
<p>Piggeries weren’t the source of the outbreak, they were the “canaries in the coalmine” – signalling the spread of the virus early on and the need to protect the broader community.</p>
<h2>What caused outbreaks in piggeries?</h2>
<p>Our <a href="https://www.sciencedirect.com/science/article/pii/S2352771423000861?via%3Dihub">research</a> <a href="https://pubmed.ncbi.nlm.nih.gov/19737082/">investigated</a> how different landscapes and weather patterns influence interactions between wildlife, mosquitoes, and outbreaks of Japanese encephalitis virus.</p>
<p>We looked at 62 piggeries where the virus had been detected and some locations where the virus had also been <a href="https://www.health.nsw.gov.au/Infectious/mosquito-borne/Pages/surveillance.aspx">detected in mosquitoes</a>, along with waterbird and feral pig habitats, rainfall and temperature.</p>
<p>Some of the results were unexpected. Piggeries were at highest risk of an outbreak when the number of different waterbird species in their location was “just right”. If there were too few or too many, the risk of an outbreak was reduced. </p>
<p>High rainfall and flooding provided excellent conditions for mosquitoes, with temporary wetlands and flooded areas posing a greater risk than permanent wetlands.</p>
<p>Temporary wetlands may have provided habitat for waterbirds whose normal habitat and movement patterns were disrupted due to the extensive La Niña flooding. </p>
<p>Or perhaps permanent wetlands support a <a href="https://link.springer.com/article/10.1007/s13157-019-01133-2">greater diversity</a> of aquatic life (including animals that eat mosquitoes) that helped keep mosquito numbers lower than temporary waterbodies.</p>
<h2>So what might happen this summer?</h2>
<p>The return of El Niño is expected to bring <a href="https://www.abc.net.au/news/2023-11-16/holder-nsw-el-nino-set-to-peak-as-one-of-the-strongest/103104264">below average rainfall and above average temperatures</a>. But that can be <a href="https://www.abc.net.au/news/2023-12-03/what-happened-to-el-nino/103179568">unpredictable</a>. Wetlands are already drying up. Bushfires have replaced floods.</p>
<p>Mosquito populations are expected to decline sharply. Surveillance programs of state and territory health authorities, such as <a href="https://www.health.nsw.gov.au/environment/pests/vector/Pages/Surveillance-and-monitoring-weekly-reports-season-2023-24.aspx">New South Wales</a> and <a href="https://www.health.vic.gov.au/infectious-diseases/mosquito-surveillance-report">Victoria</a>, are already reporting mosquito populations far lower than previous seasons.</p>
<p>So we may not see as much Japanese encephalitis this season. But that doesn’t mean it will disappear completely. </p>
<p>It doesn’t matter how hot and dry it gets, mosquitoes are resilient and will persist. They’ll seek out the same environments where water remains. So too will waterbirds and feral pigs. </p>
<p>Authorities are also on alert for the return of <a href="https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1005070">Ross River virus</a> along the coast. Despite the lower rainfall, the mosquitoes that live in saltwater wetlands will thrive following flooding by high tides, especially “<a href="https://media.bom.gov.au/social/blog/1603/explainer-king-tides/">king tides</a>”.</p>
<p>Combined with extreme weather, even during hot and dry summers, outbreaks of Ross River virus <a href="https://www.sciencedirect.com/science/article/pii/S1326020023000328">can occur</a>.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-australian-wildlife-spread-and-suppress-ross-river-virus-107267">How Australian wildlife spread and suppress Ross River virus</a>
</strong>
</em>
</p>
<hr>
<h2>How can you reduce your chance of getting these viruses?</h2>
<p>To protect yourself and family from mosquito bites and mosquito-borne disease:</p>
<ul>
<li><p>keep following the advice of health authorities</p></li>
<li><p>try to avoid bushland and wetland areas in late afternoon and early evening</p></li>
<li><p>cover up with <a href="https://theconversation.com/mozzie-repellent-clothing-might-stop-some-bites-but-youll-still-need-a-cream-or-spray-107266">long-sleeved shirts, long pants</a> and covered shoes</p></li>
<li><p>apply a <a href="https://theconversation.com/mozzies-biting-heres-how-to-choose-a-repellent-and-how-to-use-it-for-the-best-protection-150183">recommended insect repellent</a> </p></li>
<li><p>check your eligibility for a <a href="https://www.health.nsw.gov.au/Infectious/jev/Pages/vaccination.aspx">Japanese encephalitis vaccination</a>.</p></li>
</ul>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/insect-repellents-work-but-there-are-other-ways-to-beat-mosquitoes-without-getting-sticky-171805">Insect repellents work – but there are other ways to beat mosquitoes without getting sticky</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/218441/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Cameron Webb and the Department of Medical Entomology, NSW Health Pathology and University of Sydney, have been engaged by a wide range of insect repellent and insecticide manufacturers to provide testing of products and provide expert advice on mosquito biology. Cameron has also received funding from local, state and federal agencies to undertake research into mosquito-borne disease surveillance and management.</span></em></p><p class="fine-print"><em><span>Michael Walsh has received funding from the Australian Research Council to investigate zoonotic diseases associated with Australian produce and from the Australian Department of Foreign Affairs and Trade to investigate antimicrobial resistance. </span></em></p><p class="fine-print"><em><span>Victoria Brookes does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>This summer is expected to be dry and hot. Here’s what that means for the risk of mosquito-borne diseases.Cameron Webb, Clinical Associate Professor and Principal Hospital Scientist, University of SydneyMichael Walsh, Senior Lecturer of Infectious Disease Epidemiology, University of SydneyVictoria Brookes, Lecturer in Epidemiology and One Health, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2164832023-10-27T14:09:00Z2023-10-27T14:09:00ZChad’s first dengue fever outbreak: what you should know<p><em>Chad has <a href="https://www.cidrap.umn.edu/dengue/chad-reports-its-first-dengue-outbreak">reported</a> its first dengue outbreak, according to the World Health Organization (WHO). The country’s health ministry declared an outbreak on 15 August and so far 1,342 suspected cases have been reported, 41 of them confirmed in the laboratory. One death was reported among the patients with lab-confirmed cases. The outbreak started in Ouaddaï province in eastern Chad, currently the outbreak epicentre. Illnesses have also been reported in three other provinces. Godfred Akoto Boafo spoke to medical entomologist Eunice Anyango Owino about the disease.</em></p>
<h2>What causes dengue fever and how does it affect people?</h2>
<p><a href="https://www.who.int/news-room/fact-sheets/detail/dengue-and-severe-dengue">Dengue fever</a> is a mosquito-borne viral disease caused by one of the four dengue virus serotypes. It is primarily transmitted by the <em>Aedes aegypti</em> mosquito and to a lesser extent the <em>Aedes albopictus</em> mosquito, mainly in the tropical and sub-tropical areas of the world. </p>
<p>Infection with one serotype provides long-term immunity to that particular serotype, but not the others. That means that, after recovery, a person can still be infected by the other three serotypes. Serotypes are groups within a single species of microorganisms, such as bacteria or viruses, which share distinctive surface structures.</p>
<p>Most infections produce only mild flu-like illness; 80% of cases are asymptomatic. But getting infected with different serotypes one after the other puts a person at a greater risk of severe dengue, also known as dengue hemorrhagic fever. It is characterised by serious internal bleeding and organ damage, and a sudden drop in blood pressure that causes shock which can be fatal. </p>
<h2>How widespread is it in the Sahel? Why is this first outbreak in Chad significant?</h2>
<p>Dengue fever has been <a href="https://pubmed.ncbi.nlm.nih.gov/37473544/">endemic in Sudan</a>, with outbreaks documented in 2010, 2013, 2017 and 2019. Unfortunately, due to years of political and civil conflicts, the control and response capacity of the public health sector in Sudan has been limited. </p>
<p>The risk of spread in the Sahel region, which includes Niger, Mali and Chad, has always been high. This is because these countries all host the suitable mosquito vectors (<em>Aedes</em>). They also share the same tropical climate with seasonal heavy rains and floods. </p>
<p>To add to the problem, countries like Chad are grappling with a massive influx of refugees and returnees from Sudan who might be carrying the disease. The epicentre of the current outbreak, the <a href="https://www.unocha.org/publications/report/chad/chad-humanitarian-update-june-2023#:%7E:text=Following%20the%20escalation%20of%20conflict%20in%20El%20Geneina,Sudanese%20border%20in%20the%20Ouadda%C3%AF%20province%20of%20Chad">province of Ouaddaï</a> at the eastern border with Sudan, hosts more than 400,000 refugees. </p>
<p>The cities at the border with Sudan are densely populated and have poor sanitation. This provides a favourable environment for the vectors to breed. </p>
<p>In addition, Chad lacks effective disease control programmes. This is its first dengue outbreak. It doesn’t have the necessary public health preparedness and response capacities. So the risk posed by this outbreak is high. </p>
<p>The movement of the <a href="https://www.who.int/emergencies/disease-outbreak-news/item/2019-DON207">returning refugees</a> has the potential to spread the outbreak in Chad and even across the border to other countries in the Sahel, the rest of Africa, and the world at large. </p>
<h2>What treatment is available?</h2>
<p>There’s currently no available treatment for dengue in the world. Timely detection and case management, especially treatment of dehydration and plasma leakage by oral or intravenous rehydration, are key in preventing severe illness and death. </p>
<p>There is an approved dengue vaccine (Dengvaxia) for use in people aged 9-45 years. But for it to be effective they must have had one infection of dengue by any of the four serotype viruses, which must be confirmed by a laboratory test. </p>
<p>The vaccine is given in three doses within 12 months and protects against all the four dengue virus serotypes with an efficacy of 80%. However, its availability in developing countries in Africa isn’t assured, although it has been licensed by several national regulatory authorities. </p>
<p>Apart from the vaccine, the only other guard against dengue fever is prevention of mosquito bites and vector control.</p>
<h2>What is the way forward in controlling the disease?</h2>
<p>More investment should be put on expanding clinical and laboratory capabilities to deal with the disease. Given that this is Chad’s first outbreak, it needs to:</p>
<ul>
<li><p>put in place standard operating procedures for clinical management of suspected and confirmed dengue cases </p></li>
<li><p>expand the capacity for early detection of cases – this could be done by procurement of rapid diagnostic tests and by alerting communities </p></li>
<li><p>strengthen disease surveillance and coordinate the response by actively finding cases. Cases within the community are likely to be underreported as dengue is unknown to the public. Also, clinicians might not be familiar with the disease presentation. It could be confused with other common fevers. </p></li>
<li><p>put in place effective vector control measures, like draining stagnant water around residential areas, cleaning and replenishing water storage containers on a weekly basis, distributing insecticide-treated nets, spraying indoors and using window and door screens.</p></li>
<li><p>strengthen surveillance to assess the vector breeding potential in containers and to monitor insecticide resistance. This is critical for selecting the most effective insecticides. </p></li>
<li><p>make communities aware of the risks of infection and how to protect themselves. Engaged communities can take ownership of the vector control strategy and adopt healthy behaviours. </p></li>
<li><p>strengthen cross-border collaboration. The current outbreak most likely spread from Sudan. The focus should be on prevention and vector control measures in border areas.</p></li>
<li><p>mobilise resources for a national contingency plan for dengue preparedness and response. And seek help from experienced organisations like the WHO.</p></li>
</ul><img src="https://counter.theconversation.com/content/216483/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Eunice Anyango Owino receives funding from National Research Fund, Kenya. </span></em></p>The Sahel region is grappling with an outbreak of the deadly mosquito-borne disease.Eunice Anyango Owino, Medical Entomologist at the School of Biological Sciences, University of NairobiLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2153352023-10-16T02:49:22Z2023-10-16T02:49:22ZFly season: what to know about Australia’s most common flies and how to keep them away<figure><img src="https://images.theconversation.com/files/553893/original/file-20231016-29-hgfpk6.jpg?ixlib=rb-1.1.0&rect=7%2C22%2C4987%2C3302&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/close-housefly-musca-domestica-2264882059">Shutterstock</a></span></figcaption></figure><p>As the days grow longer and temperatures climb, we’re greeted by a familiar chorus of buzzing. It’s fly season again. </p>
<p>This year is off to a bumper start, with <a href="https://www.9news.com.au/national/flies-sydney-influx-insects/ecb6696a-2aea-4da9-bc32-5f194ce2ea00">bush flies swarming beach-goers</a>, <a href="https://www.ashburton.wa.gov.au/news/residents-alerted-to-increased-march-fly-activity/1542">March flies on the march</a>, and <a href="https://www.portnews.com.au/story/8045459/virus-warning-as-mosquito-numbers-explode/">mosquitoes taking to the skies</a> en masse.</p>
<p>But with almost a million species worldwide and some 30,000 calling Australia home, the (<a href="https://media.bom.gov.au/releases/1177/warmer-and-drier-spring-forecast-after-warmest-winter-on-record/">unusually</a>) warm weather also presents an opportunity to appreciate these remarkable and essential insects with whom we share our world.</p>
<p>Despite their sheer diversity, we’re likely to encounter only a select few flies daily. So who are these curious insects, and how should we think about their presence in our lives?</p>
<h2>Familiar faces</h2>
<p><a href="https://en.wikipedia.org/wiki/Musca_vetustissima">Bush flies</a> (<em>Musca vetustissima</em>) are the iconic Australian fly, and are found country-wide. They slake their thirst on the sweat and tears of mammals and so linger around our heads, shoulders and faces in search of a refreshing drink. </p>
<p>They’re so persistent that they’re credited with inspiring the “<a href="https://en.wikipedia.org/wiki/Aussie_salute">Aussie salute</a>”. These small explorers are otherwise harmless, and pose no serious threat to health or home beyond being a mild nuisance. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/553878/original/file-20231015-19-1l4j90.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A photo of a man in an Australian flag hat waving his hand in front of his face." src="https://images.theconversation.com/files/553878/original/file-20231015-19-1l4j90.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/553878/original/file-20231015-19-1l4j90.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=398&fit=crop&dpr=1 600w, https://images.theconversation.com/files/553878/original/file-20231015-19-1l4j90.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=398&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/553878/original/file-20231015-19-1l4j90.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=398&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/553878/original/file-20231015-19-1l4j90.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=500&fit=crop&dpr=1 754w, https://images.theconversation.com/files/553878/original/file-20231015-19-1l4j90.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=500&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/553878/original/file-20231015-19-1l4j90.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=500&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The ‘Aussie salute’ is a characteristic gesture of waving flies – specifically the persistent Australian bush flies – away from the face.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Aussie_salute#/media/File:Aussie_salute.jpg">Mick and Rortles / Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Similar in appearance are <a href="https://en.wikipedia.org/wiki/Housefly">house flies</a> (<em>Musca domestica</em>), which frequent our homes. Unlike bush flies, however, they’re more interested in scraps of food and waste left unprotected. They regurgitate digestive juices to break solids into a mush more amenable to their straw-like mouths, and can pose a minor hygiene concern as a consequence.</p>
<p><a href="https://en.wikipedia.org/wiki/Calliphoridae">Blowflies</a> bring some sparkle to the fly world, and are easily recognised by their often large, shiny bodies. Although sometimes a pest, they’re also voracious scavengers and effective pollinators. In this way they do their bit to break down organic matter, recycle nutrients, and transport pollen to support plant life.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/553895/original/file-20231016-21-m2xrcy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A photo of a sparkly, metallic blue fly perched on a green leaf or stem." src="https://images.theconversation.com/files/553895/original/file-20231016-21-m2xrcy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/553895/original/file-20231016-21-m2xrcy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=398&fit=crop&dpr=1 600w, https://images.theconversation.com/files/553895/original/file-20231016-21-m2xrcy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=398&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/553895/original/file-20231016-21-m2xrcy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=398&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/553895/original/file-20231016-21-m2xrcy.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=500&fit=crop&dpr=1 754w, https://images.theconversation.com/files/553895/original/file-20231016-21-m2xrcy.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=500&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/553895/original/file-20231016-21-m2xrcy.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=500&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The golden bluebottle (Chrysomya incisuralis) is one of many species of Australian blowfly.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/australian-golden-bluebottle-blowfly-known-chrysomya-1676775739">Shutterstock</a></span>
</figcaption>
</figure>
<p>The sheer size of <a href="https://en.wikipedia.org/wiki/Tabanidae">horseflies</a> makes them powerful fliers, which can often be heard and seen at a distance. Females demand a blood meal and so pack a hearty bite to mammals, including us, and can be a nuisance to livestock. They are also, however, excellent pollinators, with <a href="https://doi.org/10.1016/j.sajb.2009.06.015">some orchids</a> relying on their hard work and specialised mouthparts for survival.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/does-zika-virus-pose-a-threat-to-australia-53557">Does Zika virus pose a threat to Australia?</a>
</strong>
</em>
</p>
<hr>
<p>Finally, and famously, are <a href="https://en.wikipedia.org/wiki/Mosquito">mosquitoes</a>. (Yes, they are a type of fly.) Many summer evenings are spent swatting females as they sip our blood. </p>
<p>More serious is their role as vectors for diseases that have <a href="https://doi.org/10.1641/B580812">helped to topple empires</a>, and which remain a significant health burden, especially in the Global South. <a href="https://doi.org/10.1016/S0140-6736(12)60034-8">Malaria</a> is among the farthest-reaching, while <a href="https://www.cdc.gov/ross-river-virus/healthcareproviders/">Ross River Virus</a>, <a href="http://www.cdc.gov/chikungunya/">chikungunya</a>, <a href="https://theconversation.com/does-zika-virus-pose-a-threat-to-australia-53557">zika</a> and <a href="http://www.cdc.gov/dengue/">dengue</a> all circulate with help from mosquitoes.</p>
<h2>Shoo fly?</h2>
<p>For the minority of flies that prove a recurring annoyance, the primary goal is to deter rather than kill them. In this case, the remedies are simple:</p>
<ul>
<li>use topical repellents containing DEET or Picaridin, and wear loose-fitting clothing when outside</li>
<li>install flyscreens in the house, and check them regularly for holes</li>
<li>keep your food covered, both at home and when out enjoying the warm weather</li>
<li>empty your bins regularly and minimise standing water, both of which can attract unwanted attention.</li>
</ul>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/the-battle-against-bugs-its-time-to-end-chemical-warfare-111629">The battle against bugs: it's time to end chemical warfare</a>
</strong>
</em>
</p>
<hr>
<p>Avoid <a href="https://theconversation.com/the-battle-against-bugs-its-time-to-end-chemical-warfare-111629">reaching for the bug-bombs and sprays</a>, which have devastating impacts on beneficial insects. If a chemical last resort is required, choose selective sprays rather than broad-spectrum options such as pyrethroids and neonicotinoids, which kill the many good bugs with the few bad ones. </p>
<p>Similarly, those noise-emitting, electrified or smelly gadgets that promise a fly-free existence are best avoided, as most are either <a href="https://theconversation.com/the-buzz-from-your-smartphone-wont-stop-mosquito-bites-92611">ineffective</a>, or harm far more than their intended targets.</p>
<h2>From pesky to paramount</h2>
<p>While our daily encounters with a handful of fly species may taint our perception of the group as a whole, such a view is both unwarranted and unjustified. Flies are among the most diverse animals on the planet, and are utterly crucial for the healthy function of our ecosystems.</p>
<p>Many, like <a href="https://en.wikipedia.org/wiki/Hover_fly">hover flies</a>, are important pollinators. In an era of pollinator declines and <a href="https://www.fao.org/documents/card/en/c/cc3017en">heightened food insecurity</a>, their ongoing work is <a href="https://doi.org/10.1080/14888386.2008.9712892">key to supporting agricultural production</a>, and plant life more generally. </p>
<figure class="align-center ">
<img alt="A photo of a skinny black fly sitting in the middle of a yellow and pink flower." src="https://images.theconversation.com/files/553897/original/file-20231016-23-cxxzcl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/553897/original/file-20231016-23-cxxzcl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=413&fit=crop&dpr=1 600w, https://images.theconversation.com/files/553897/original/file-20231016-23-cxxzcl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=413&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/553897/original/file-20231016-23-cxxzcl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=413&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/553897/original/file-20231016-23-cxxzcl.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=519&fit=crop&dpr=1 754w, https://images.theconversation.com/files/553897/original/file-20231016-23-cxxzcl.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=519&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/553897/original/file-20231016-23-cxxzcl.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=519&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The larvae of the black soldier fly (Hermetia illucens) are highly effective decomposers, eating twice their own bodyweight every day.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/Hermetia_illucens#/media/File:Hermetia_illucens_MHNT_Fronton.jpg">Didier Descouens / Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>On the other side of the circle of life are outstanding decomposers, such as <a href="https://en.wikipedia.org/wiki/Hermetia_illucens">black soldier flies</a>. Each individual larva can eat twice its bodyweight daily, which at the scale of tens of thousands of grubs presents a promising pathway towards sustainable waste management. They are also a rich source of protein for livestock, <a href="https://theconversation.com/food-for-thought-feeding-our-growing-population-with-flies-64374">or even humans</a>.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/food-for-thought-feeding-our-growing-population-with-flies-64374">Food for thought: feeding our growing population with flies</a>
</strong>
</em>
</p>
<hr>
<p>Just as a very few flies are pests, many serve as remedies in their role as biological controls. The 10,000-odd species of <a href="https://en.wikipedia.org/wiki/Tachinidae">tachinid</a>, or example, make a living as parasitoids of other insects. That is, they lay their eggs inside, and eventually kill, the developing young of others, which include pest caterpillars, flies and bugs.</p>
<p>Moreover, flies have proven invaluable in <a href="https://theconversation.com/trust-me-im-an-expert-forensic-entomology-or-what-bugs-can-tell-police-about-when-someone-died-124416">forensics</a>, <a href="https://doi.org/10.1038/35042080">medicine and scientific research</a>, and <a href="https://doi.org/10.3389/fenvs.2023.1146052">environmental monitoring</a>, underscoring how deeply our lives intertwine with theirs. </p>
<h2>Fly on</h2>
<p>As the warm weather rolls around, then, take the opportunity to look a little closer at our nimble neighbours, and consider both their <a href="https://dx.doi.org/10.1111/j.1469-185X.2007.00018.x">staggering diversity</a> and the vital roles they humbly fill. The natural world – us included – would not be the same without them.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/trust-me-im-an-expert-forensic-entomology-or-what-bugs-can-tell-police-about-when-someone-died-124416">Trust Me, I'm An Expert: forensic entomology, or what bugs can tell police about when someone died</a>
</strong>
</em>
</p>
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<img src="https://counter.theconversation.com/content/215335/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Thomas White receives funding from The Australian Research Council, Agrifutures, and the Hermon Slade Foundation. He is also affiliated with the conservation charity Invertebrates Australia. </span></em></p><p class="fine-print"><em><span>Tanya Latty receives funding from the Australian Research Council and AgriFutures Australia. She is affiliated with conservation organisation Invertebrates Australia and is president of the Australasian Society for the Study of Animal Behaviour. </span></em></p>Early warm weather has triggered a bumper season for Australia’s 30,000 fly species.Thomas White, Senior lecturer, University of SydneyTanya Latty, Associate professor, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2150082023-10-06T15:47:18Z2023-10-06T15:47:18ZDengue: why is this sometimes fatal disease increasing around the world?<p>Something unusual seems to be happening with dengue, a potentially fatal mosquito-borne viral disease found across swathes of tropical Africa, Asia and the Americas. As with most infectious diseases, the number of cases tends to rise and fall over the years as epidemics come and go, but recently changes seem to be afoot in how dengue is behaving. </p>
<p>Not only is the number of new infections <a href="https://news.un.org/en/story/2023/07/1138962#:%7E:text=Cases%20rising%20fast,more%20and%20more%20accurate%20figures.%E2%80%9D">steadily rising around the world</a>, but outbreaks are becoming larger and less predictable. For example, 2019 saw the <a href="https://www.who.int/news-room/fact-sheets/detail/dengue-and-severe-dengue">greatest number of dengue fever cases ever recorded</a> – almost twice as high as the previous year. And in July 2023, there were a <a href="https://www.aljazeera.com/news/2023/10/2/bangladesh-dengue-deaths-cross-1000-in-worst-outbreak-on-record">record number of deaths</a> from the disease in Bangladesh. </p>
<p>Most people infected with dengue will suffer from <a href="https://www.cdc.gov/dengue/symptoms/index.html">flu-like symptoms</a>, ranging from relatively mild to very unpleasant, with fever, headache and joint pain. </p>
<p>In more severe cases, though, blood vessels can become damaged by the virus, allowing blood to leak into the surrounding tissues. This condition, known as <a href="https://www.msdmanuals.com/en-gb/professional/infectious-diseases/arboviruses,-arenaviridae,-and-filoviridae/dengue-hemorrhagic-fever-dengue-shock-syndrome">dengue haemorrhagic fever</a>, can produce bruising, and bleeding from the nose and gums. It can ultimately lead to organ failure and death as the body slips into shock.</p>
<p>The principal agent, or vector, in the transmission of dengue, is the Asian Tiger mosquito <em>Aedes aegypti</em>, although its cousin <em>Aedes albopictus</em> is also capable of spreading the virus. </p>
<figure class="align-center ">
<img alt="Aedes aegypti mosquito on human skin" src="https://images.theconversation.com/files/552539/original/file-20231006-25-sfj0l7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/552539/original/file-20231006-25-sfj0l7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/552539/original/file-20231006-25-sfj0l7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/552539/original/file-20231006-25-sfj0l7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/552539/original/file-20231006-25-sfj0l7.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/552539/original/file-20231006-25-sfj0l7.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/552539/original/file-20231006-25-sfj0l7.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"><em>Aedes aegypti</em> mosquitoes are the main spreaders of dengue.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/zica-virus-aedes-aegypti-mosquito-on-369189926">Tacio Philip Sansonovski/Shutterstock</a></span>
</figcaption>
</figure>
<p>While <em>Aedes aegypti</em> is essentially a tropical mosquito, it is a very adaptable insect. In recent years, it has expanded its range out of the tropics into <a href="https://theconversation.com/dengue-in-france-tropical-diseases-in-europe-may-not-be-that-rare-for-much-longer-191033">southern Europe</a> and to <a href="https://www.cdc.gov/dengue/areaswithrisk/in-the-us.html">several states</a> in the US, including Florida, Hawaii, Texas and Arizona.</p>
<p>All mosquitos need water to breed, but another thing that has helped in its migration is its ability to use even the smallest of water containers to do so, something as small as a discarded plastic bottle cap will do. </p>
<p>Despite this capability, it is usually the lack of breeding sites that caps the number of mosquitoes in circulation and therefore their ability to spread the dengue virus. But in Bangladesh this year the rains arrived early and, coupled with an unusually high temperature and humidity, this led <a href="https://www.reuters.com/business/healthcare-pharmaceuticals/bangladesh-dengue-deaths-top-1000-worst-outbreak-2023-10-02/">mosquito numbers to surge</a>. </p>
<p>Because a large proportion of the population of Bangladesh spends a great deal of time outside and tends to have houses that are relatively simple for mosquitoes to enter, it took little time at all for dengue to take hold and then explode. </p>
<p>Although no one is certain about what’s driving the increase and instability of dengue, climate change may be contributing as much of the world is getting both warmer and wetter.</p>
<p>Fortunately for most high-income countries, even areas within the current range of <em>Aedes Aegypti</em>, climate change will probably not lead to any major outbreaks simply because people spend so much of their time indoors and out of the reach of mosquitos. It takes a certain amount of biting pressure within a population to sustain transmission. </p>
<h2>WHO warns of dengue spread to new places</h2>
<p>However, a <a href="https://www.reuters.com/business/healthcare-pharmaceuticals/dengue-will-take-off-southern-europe-us-africa-this-decade-who-scientist-says-2023-10-06/">new report</a> by the World Health Organization’s chief scientist suggests that the disease may still be able to establish itself in parts of Europe, the US and Africa where it has previously been absent. </p>
<p>Something that is also likely to be seen more often is what happened recently in Bangladesh repeats itself across similar middle- and low-income countries where the opportunity for mosquitoes and people to mix is greater. </p>
<p>The solution is likely to be an affordable and effective vaccine. Indeed, the WHO has recently <a href="https://www.who.int/news/item/05-10-2023-message-by-the-director-of-the-department-of-immunization--vaccines-and-biologicals-at-who---september-2023">recommended the Qdenga vaccine for children</a> living in areas where the infection is a major public health problem. </p>
<p>However, dengue is not the only concern as there are a variety of other mosquito-borne infections that kill around a million people every year. Diseases like <a href="https://www.who.int/news-room/fact-sheets/detail/chikungunya">chikungunya</a>, <a href="https://www.who.int/news-room/fact-sheets/detail/yellow-fever">yellow fever</a> and Zika virus are all transmitted by <em>Aedes aegypti</em>. </p>
<p>An increasingly warmer, wetter and less reliable climate is therefore probably going to be the precursor for many more – and less predictable – mosquito-related disease outbreaks, and ultimately deaths, in the future. As with most other life-threatening communicable diseases, it is once again the poorest communities in the global tropics that will have to bear the brunt of this.</p><img src="https://counter.theconversation.com/content/215008/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Simon Bishop does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Something unusual seems to be happening with dengue, a potentially fatal mosquito-borne viral disease.Simon Bishop, Associate Professor, Faculty of Health, Anglia Ruskin UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2147982023-10-03T19:50:49Z2023-10-03T19:50:49Z‘We could eradicate malaria by 2040’ says expert after revolutionary vaccine is approved by WHO<p><em>The World Health Organization has <a href="https://www.who.int/news/item/02-10-2023-who-recommends-r21-matrix-m-vaccine-for-malaria-prevention-in-updated-advice-on-immunization">approved</a> a new vaccine that scientists argue will be a game-changer in the fight against malaria, which kills half a million people in Africa every year. Trials have shown that the <a href="https://www.ox.ac.uk/news/2023-10-02-oxford-r21matrix-m-malaria-vaccine-receives-world-health-organization-recommendation">R21/Matrix vaccine</a>, developed by Oxford University together with the Serum Institute of India, reduces malaria by up to 75%. It can be manufactured cheaply and on a mass scale. The Conversation Weekly spoke to chief investigator Adrian Hill, who is also director of the Jenner Institute at the University of Oxford, about this revolutionary vaccine. Below are edited excerpts from the <a href="https://theconversation.com/the-long-road-to-a-new-malaria-vaccine-told-by-the-scientists-behind-the-breakthrough-podcast-214885">podcast</a>.</em></p>
<hr>
<h2>Why is the R21/Matrix vaccine a game-changer?</h2>
<p>We’re seeing about 75% efficacy by counting the reduction in numbers of malaria episodes over a year. The best vaccine prior to this was about 50% over a year, and lower than that over three years.</p>
<p>This is a material improvement, but that’s not the main improvement. The big difference is how you can manufacture it at a scale that is really needed to protect most of the children who need a malaria vaccine in Africa. </p>
<p>There are about 40 million children born every year in malaria areas in Africa who would benefit from a vaccine. Ours is a four-dose vaccine over 14 months, so you need about 160 million doses. We can achieve that. </p>
<p>The Serum Institute of India, our manufacturing and commercial partner, can produce hundreds of millions of doses of this vaccine each year, whereas the previous vaccine could be manufactured at a scale of six million doses a year from 2023 to 2026, according to Unicef reports. </p>
<p>The third real advantage of this vaccine is its cost. We were well aware that we couldn’t produce a US$100 vaccine. It wouldn’t fly for international agencies supporting the purchase and distribution of the vaccine in very low-income countries.</p>
<p>So where we are now is a price that’ll vary according to the scale, but at high volume it should be US$5 a dose.</p>
<h2>Why has developing a malaria vaccine been so difficult?</h2>
<p>People have been trying to make malaria vaccines for over 100 years. Well over 100 vaccines have gone into clinical trials in people. Very, very few have worked to any degree.</p>
<p>Malaria is not a virus, it’s not a bacterium. It’s a protozoan parasite, some thousands of times larger than a typical virus. A good measure of that is how many genes it has. Covid has 13, malaria has about 5,500. This is one of the reasons that malaria is super complex.</p>
<p>There are different parasite forms the first of which are injected by the mosquito into the skin and rapidly go to the liver. They spend a week multiplying there, and then they go into the bloodstream. And they are hugely different during these different stages. And the parasites grow at a rate of tenfold every 48 hours, multiplying furiously. </p>
<p>By the time they get to a really high parasite density, you will be very unwell. Or if you’re unlucky, you will die, typically from cerebral symptoms, a coma or from being severely anaemic. The parasites break open the red blood cells.</p>
<p>And then there’s yet another stage where the parasite changes again to a form that the mosquito can take up through its next bite and continue the life cycle by infecting somebody else.</p>
<p>So this is as complex as it gets with infectious pathogens.</p>
<p>Malaria typically goes through four life cycles and they’re all different. If you can get a really good vaccine for one of those, you will break the cycle of transmission. And that’s what we’ve been trying to do.</p>
<p>We’ve been working on targeting the so-called sporozoites, which is the form that the mosquito inoculates into your skin. We’re trying to trap it before it can get to the liver and carry on the life cycle.</p>
<p>Luckily, there are no symptoms of malaria at that stage. It’s a silent infection until it gets into the blood and starts multiplying inside your red blood cells. </p>
<p>So the sporozoite is a natural target to try and kill the parasite before it multiplies very quickly.</p>
<h2>Tell us about past attempts to develop a malaria vaccine</h2>
<p>Very early on people tried to use the whole microbe in the same way that vaccine pioneer Edward Jenner used the whole virus to inoculate against smallpox. Then the French microbiologist Louis Pasteur came along with bacterial vaccines, and so on.
In about 1943, there was a trial of the whole malaria parasite vaccine candidate in New York with zero efficacy. That put people off for a while.</p>
<p>It wasn’t until the 1980s when we could actually begin to sequence the genes in the parasite that new vaccination candidates appeared. And then within 10 years we had 5,000 candidates because everyone hoped that the gene they had sequenced might be a malaria vaccine. And of course almost all of those failed.</p>
<h2>Why aren’t vaccines for whole parasites effective against malaria?</h2>
<p>It’s the same reason that just getting infected once by malaria doesn’t give you protection against the next infection. </p>
<p>In the areas of malaria where we test our vaccines in Africa, some children get up to eight episodes in three or four months. They get quite unwell with the first and three weeks later they’re having a second bout and so on. Natural immunity doesn’t work until you’ve had a lot of different infections and that’s why adults are generally protected against malaria and don’t become very unwell. </p>
<p>The people who die of malaria in an endemic area are the <a href="https://www.who.int/news-room/fact-sheets/detail/malaria">young children </a> who may never have been infected before and die with their first infection when they’re one year old, or they might have had one or two episodes, but that wasn’t enough to give them sterilising immunity.</p>
<p>Malaria has been around for tens of millions of years. Not just in humans, but in the species that we were before we became humans.</p>
<p>It’s a very wily parasite and has developed <a href="https://academic.oup.com/femsre/article/40/2/208/2570118">immune escape mechanisms </a> of all sorts.</p>
<p>When you try to vaccinate, you suddenly find there’s some way the parasite gets around that, and it’s only when you get up to really extraordinarily high levels of antibodies that the parasite hasn’t seen before and hasn’t learnt to evolve against that it becomes effective.</p>
<h2>Will we ever eradicate malaria entirely?</h2>
<p>Malaria is very high on the list of diseases we want to eradicate. I don’t think it’s going to happen in five years or 10 years, but it should happen in something like 15 years. So 2040 would be a reasonable target. </p>
<p>Nobody’s suggesting we stop doing what we’re doing at the moment with bed nets and spraying and drugs. But now we have a new tool that may be individually more protective than any of the tools we’re using at the moment.</p><img src="https://counter.theconversation.com/content/214798/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Adrian Hill receives funding from government and charitable funders of malaria vaccine development. He has received funding awarded to the University of Oxford from the Serum Institute of India to support clinical trials of the R21/Matrix-M vaccine. He may benefit for a share of any royalty stream to Oxford University from the vaccine.</span></em></p>People have been trying to make malaria vaccines for over 100 years. With the help of the revolutionary new R21/Matrix vaccine the disease could be eradicated by 2040.Adrian Hill, Director of the Jenner Institute, University of OxfordLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2129552023-09-17T12:07:36Z2023-09-17T12:07:36ZWhat Canadians need to know about West Nile virus, a mosquito-borne infection that can be life-threatening<iframe style="width: 100%; height: 100px; border: none; position: relative; z-index: 1;" allowtransparency="" allow="clipboard-read; clipboard-write" src="https://narrations.ad-auris.com/widget/the-conversation-canada/what-canadians-need-to-know-about-west-nile-virus-a-mosquito-borne-infection-that-can-be-life-threatening" width="100%" height="400"></iframe>
<p>During the late summer of 1999, New York City recorded an <a href="https://doi.org/10.2105%2Fajph.92.8.1218">unusual number of cases of encephalitis</a> (inflammation of the brain). At the same time, the <a href="https://www.nationalgeographic.com/science/article/west-nile-virus-the-stranger-that-came-to-stay">Bronx Zoo</a> reported a massive death of birds and mammals. </p>
<p>The human encephalitis cases might have been attributed to a flare-up of an endemic arbovirus (<a href="https://ndc.services.cdc.gov/case-definitions/arboviral-diseases-neuroinvasive-and-non-neuroinvasive-2015/">a virus transmitted by a tick or mosquito bite</a>) such as <a href="https://www.cdc.gov/sle/index.html">St. Louis encephalitis</a>, but the concurrent bird and mammal deaths suggested the human illnesses warranted further investigation. </p>
<p>Scientists eventually identified these as the first confirmed cases of West Nile virus (WNV) in North America.</p>
<h2>West Nile virus in North America</h2>
<p>WNV was first reported in a woman with a fever in Uganda in 1937. An <a href="https://doi.org/10.2214/ajr.184.3.01840957">outbreak in Israel in 1957</a> established WNV as a cause of <a href="https://doi.org/10.3201/eid0704.017416">severe meningoencephalitis</a> (inflammation of the spinal cord and brain) in elderly patients. </p>
<p>Several clusters or medium-range outbreaks were reported from Asia, Europe and Africa in the 20th century. Finally, the virus managed to cross the Atlantic and landed in North America in 1999.</p>
<figure class="align-center ">
<img alt="Round blue particles nestled in a red matrix" src="https://images.theconversation.com/files/548213/original/file-20230914-19-x6rm98.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/548213/original/file-20230914-19-x6rm98.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=454&fit=crop&dpr=1 600w, https://images.theconversation.com/files/548213/original/file-20230914-19-x6rm98.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=454&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/548213/original/file-20230914-19-x6rm98.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=454&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/548213/original/file-20230914-19-x6rm98.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=570&fit=crop&dpr=1 754w, https://images.theconversation.com/files/548213/original/file-20230914-19-x6rm98.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=570&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/548213/original/file-20230914-19-x6rm98.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=570&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Microscopic view of West Nile virus particles in a cell.</span>
<span class="attribution"><span class="source">(NIAID)</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>In 1999, the <a href="https://www.cdc.gov/westnile/statsmaps/historic-data.html">case number</a> was limited to 62 in New York City, and there was concern about a huge surge in 2000. Fortunately, the case number in 2000 was 21, which is exceedingly low, but it had spread to New Jersey and Connecticut. The case number remained in a similar low range (only 66 cases) in 2001. </p>
<p>However, the virus hit hard the following year. In 2002, the case number rose to over 4,000 in the United States. The same year, <a href="https://www.canada.ca/en/public-health/services/diseases/west-nile-virus/surveillance-west-nile-virus.html">Canada experienced its first cases</a> in Ontario.</p>
<p>The U.S. has reported a <a href="https://www.cdc.gov/westnile/statsmaps/historic-data.html">cumulative total</a> of 56,569 cases and 2,773 deaths, while <a href="https://www.canada.ca/en/public-health/services/diseases/west-nile-virus/surveillance-west-nile-virus.html#a1">Canada has reported 6,683 cases</a> and about 150 deaths (I’m told by the Centre for Food-borne, Environmental & Zoonotic Infectious Diseases, Public Health Agency of Canada), with the highest number of cases observed in the U.S. in 2003 and in Canada in 2007.</p>
<p>This virus spread across the entire continent very quickly, and covered most of North America by 2005. However, it took almost 10 years for the virus to <a href="https://doi.org/10.1089/vbz.2010.0062">show up in British Columbia</a>. In Canada, most of the cases were found in the Prairie region (Alberta, Saskatchewan and Manitoba). <a href="https://www.cdc.gov/westnile/statsmaps/historic-data.html">In the U.S.</a>, Midwestern states have been most affected.</p>
<p>West Nile virus is an RNA virus, a close cousin of <a href="https://www.who.int/news-room/fact-sheets/detail/dengue-and-severe-dengue">Dengue</a>, <a href="http://www.bccdc.ca/health-info/diseases-conditions/yellow-fever">Yellow fever</a>, St. Louis encephalitis and <a href="http://www.bccdc.ca/health-info/diseases-conditions/zika-virus">Zika virus</a>, to name a few. It belongs to the family Flaviviridae. </p>
<h2>Symptoms and transmission</h2>
<p><a href="https://www.cdc.gov/westnile/symptoms/index.html">Approximately 80 per cent of people</a> exposed to WNV are asymptomatic. <a href="https://doi.org/10.14745/ccdr.v40i10a01">The incubation period</a> in humans is about a week; however, this ranges from two to 15 days after the virus enters the body.</p>
<p>Among symptomatic individuals, all of them experience fever, and many also experience headaches, body aches, a mild rash and swollen lymph glands to varying degrees. </p>
<p>Although most cases go unnoticed, the virus still has deadly potential. <a href="https://nccid.ca/debrief/west-nile-virus/">A small number of people</a> (around one per cent) experience severe symptoms, including encephalitis. However, over the years, the <a href="https://doi.org/10.1038/ncpneuro0176">number of neurological cases has been increasing</a>.</p>
<p>This virus is mostly <a href="https://www.who.int/news-room/fact-sheets/detail/west-nile-virus">transmitted via mosquito bites</a>; however, very rarely it could transmit via blood transfusion, organ or tissue transplants, from mother to unborn babies and through exposure to infected animals. </p>
<p>A number of birds, predominantly corvids such as crows, jays and magpies, act as reservoirs as well as <a href="https://www.biologyonline.com/dictionary/amplifier-host">amplifying hosts</a>. When an uninfected mosquito feeds on an infected bird and then bites a healthy human, the human becomes infected. </p>
<p>Humans are considered dead-end hosts, meaning that even if a mosquito feeds on an infected individual, that mosquito cannot transmit the virus to another individual <a href="https://www.who.int/news-room/questions-and-answers/item/dengue-and-severe-dengue">as can happen with the dengue virus</a>.</p>
<p>Once people are severely infected with West Nile virus, they <a href="https://www.cdc.gov/westnile/symptoms/index.html">acquire longer immunity</a>. Older people are usually at high risk for severe infection due to underlying health conditions. People with diabetes and uncontrolled hypertension <a href="https://www.canada.ca/en/public-health/services/diseases/west-nile-virus/risks-west-nile-virus.html">have a greater risk</a> of developing severe neurological disease from the West Nile virus. </p>
<h2>Diagnosis</h2>
<p>Patients who become ill with a fever and severe headache within a few days of a mosquito bite should visit their family physician or any health-care facility.</p>
<p>Because WNV is closely related to other pathogens, diagnosis is often challenging.
Patient signs and symptoms, history of mosquito bites and laboratory tests are all important when assessing patients for possible infection with West Nile virus.</p>
<p>The most common <a href="https://www.publichealthontario.ca/en/Laboratory-Services/Test-Information-Index/West-Nile-Virus-Serology">laboratory test</a> is to detect antibodies against WNV in the blood. However, WNV antibodies cross-react with dengue, Zika or other flaviviruses, so if this test is positive, an additional test is required to confirm the diagnosis. </p>
<p>This additional test is called the Plaque Reduction Neutralization Test or PRNT for short. It requires a live virus, so it must be done in a containment level 3 (CL3) laboratory. </p>
<p>The laboratory can also diagnose viral RNA using molecular tests, but interestingly, the virus often disappears from the blood when people exhibit symptoms. For encephalitic patients, cerebrospinal fluid can be used to detect the virus using molecular methods such as a polymerase chain reaction (PCR) test.</p>
<h2>Preventive measures</h2>
<p>There is no human vaccine for the West Nile virus. The most important preventive measure to avoid West Nile virus infection is to avoid mosquito bites. This seems simple but is often very challenging. </p>
<figure class="align-center ">
<img alt="Close-up view of a mosquito held with tweezers" src="https://images.theconversation.com/files/548224/original/file-20230914-17-vsdb54.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/548224/original/file-20230914-17-vsdb54.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/548224/original/file-20230914-17-vsdb54.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/548224/original/file-20230914-17-vsdb54.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/548224/original/file-20230914-17-vsdb54.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/548224/original/file-20230914-17-vsdb54.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/548224/original/file-20230914-17-vsdb54.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">A Culex tarsalis mosquito, a species that can transmit West Nile virus to humans, and is found across Canada.</span>
<span class="attribution"><span class="source">(AP Photo/Rick Bowmer)</span></span>
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<p>People should use common sense during outdoor and indoor activities. Mosquito bites can be prevented by using bug spray, wearing protective clothing and avoiding areas that may have mosquitoes during the times when the species is most active, typically dusk and dawn. </p>
<p>A few species of mosquitoes can transmit WNV to humans. Among these, two of the most common species — the Culex pipiens and Culex tarsalis — are found across Canada, and their habitat is <a href="https://ncceh.ca/resources/evidence-reviews/impacts-canadas-changing-climate-west-nile-virus-vectors">predicted to expand with climate change</a>. Mosquitoes not only transmit WNV, but also transmit <a href="https://www.canada.ca/en/public-health/services/laboratory-biosafety-biosecurity/pathogen-safety-data-sheets-risk-assessment/california-serogroup-pathogen-safety-data-sheet.html">California serogroup viruses</a>, which cause encephalitis, as well as <a href="https://www.canada.ca/en/public-health/services/laboratory-biosafety-biosecurity/pathogen-safety-data-sheets-risk-assessment/eastern-equine-encephalitis.html">eastern equine encephalitis</a> viruses. </p>
<p>There is also no specific treatment for West Nile virus; medical management is supportive. Patients with severe symptoms often require pain control for headaches and medication and rehydration to treat nausea and vomiting. </p>
<p><a href="https://www.canada.ca/en/public-health/services/diseases/west-nile-virus/surveillance-west-nile-virus/west-nile-virus-weekly-surveillance-monitoring.html">So far in 2023</a>, only a <a href="https://www.cbc.ca/news/canada/hamilton/hamilton-west-nile-virus-2023-1.6957260">few human cases</a> have been identified in Ontario. However, a few mosquito pools in Manitoba and Ontario also tested positive, and also a few WNV-positive birds were found in Saskatchewan, Manitoba, Ontario and Québec.</p>
<p>No matter how many cases we are seeing, everyone is advised to take precautions against mosquito bites to avoid these life-threatening diseases.</p><img src="https://counter.theconversation.com/content/212955/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Muhammad Morshed does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>West Nile virus arrived in North America in 1999 and spread across the continent by 2005. Here’s what you need to know about this mosquito-borne pathogen.Muhammad Morshed, Clinical Professor, Department of Pathology and Laboratory Medicine, University of British ColumbiaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2127112023-09-12T01:50:29Z2023-09-12T01:50:29ZIt’s warming up and mozzies are coming. Here’s how to mosquito-proof your backyard<figure><img src="https://images.theconversation.com/files/547382/original/file-20230911-29-86sa9t.JPG?ixlib=rb-1.1.0&rect=14%2C402%2C4778%2C2737&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">A/Prof Cameron Webb (NSW Health Pathology)</span></span></figcaption></figure><p>The weather is warming up and that means more time in the backyard. It also means more mosquitoes. </p>
<p>Here are five ways you can mosquito-proof your backyard that <a href="https://theconversation.com/the-battle-against-bugs-its-time-to-end-chemical-warfare-111629">don’t rely on spraying insecticides</a>.</p>
<h2>1. Get rid of water</h2>
<p>Mosquitoes need water to complete their life cycles. They <a href="https://theconversation.com/feel-like-youre-a-mozzie-magnet-its-true-mosquitoes-prefer-to-bite-some-people-over-others-128788">need blood</a> – but water and warmth are just as important.</p>
<p>Getting rid of water around your backyard will go a long way to keeping mosquitoes away. Water trapped in blocked roof gutters, drains and tarpaulin covering boats and trailers can be a great home for mosquitoes. </p>
<p>Mosquitoes can exploit the tiniest of water sources too. It may just be the upturned lid of a discarded plastic drink bottle. If it traps water, mosquitoes will find it and lay eggs in it.</p>
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Read more:
<a href="https://theconversation.com/how-can-the-bite-of-a-backyard-mozzie-in-australia-make-you-sick-171601">How can the bite of a backyard mozzie in Australia make you sick?</a>
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<p>Flush out your bird bath once a week to disrupt the mosquito’s life cycle. </p>
<p>If you have a pond, installing a fountain will discourage mosquitoes. If you can’t keep water clean and circulating, consider filling it with sand and gravel to create an interesting garden bed for succulents or other plants.</p>
<p>Mosquitoes will avoid clean and chlorinated swimming pools but will quickly move into “green pools”. If you’re not using your pool, consider <a href="https://www.krg.nsw.gov.au/Environment/Your-local-environment/Wildlife/Living-with-wildlife/Pool-to-pond/How-to-convert-your-pool">converting it to a “pond”</a> so that fish can help keep mosquito numbers down.</p>
<h2>2. Screen up – windows, doors and rainwater tanks</h2>
<p>If you can’t get rid of permanent water, at least stop mosquitoes getting to it (or you).</p>
<p>Ensure <a href="https://www.brisbane.qld.gov.au/clean-and-green/natural-environment-and-water/water/water-smart-homes/rainwater-tanks/using-your-rainwater-tank">rainwater and septic tanks</a> have screens to stop mosquitoes entering.</p>
<p>Screen windows and doors to stop mosquitoes entering the home. There are plenty of flexible screening options for windows, doors and balconies.</p>
<p>If you live in a mosquito-prone area, creating a screened outdoor area (such as a pergola, courtyard, or balcony) will give you the opportunity to spend time outdoors without being hassled by mozzies.</p>
<h2>3. Choose your garden plants carefully</h2>
<p>Some plants <a href="https://bioone.org/journals/Journal-of-the-American-Mosquito-Control-Association/volume-25/issue-3/09-0016.1/Are-Commercially-Available-Essential-Oils-from-Australian-Native-Plants-Repellent/10.2987/09-0016.1.short">contain essential oils and other chemicals</a> that, when extracted and concentrated, provide protection against biting mosquitoes. But there isn’t a lot of evidence that the whole plant will keep mosquitoes away from your garden.</p>
<p>Some types of plants are even marketed as “mozzie blockers” or “mosquito repelling”. But there isn’t <a href="https://www.veranda.com/outdoor-garden/a40592197/do-mosquito-repelling-plants-work/">any evidence of effectiveness</a>. In fact, some of these plants, <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/j.1440-6055.2009.00736.x">such as melaleucas</a>, also happen to be associated with <a href="https://academic.oup.com/jme/article/36/4/515/903838">hot spots of mosquito breeding</a> in coastal Australia.</p>
<p>The plants to <em>avoid</em> around the home are those that help mosquitoes breed, such as <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1440-6055.2008.00641.x">bromeliads</a>, which trap water. </p>
<h2>4. Encourage the animals that eat mosquitoes</h2>
<p>Mosquitoes are food for a range of animals including birds, bats, fish, frogs, lizards, insects, spiders and <a href="https://besjournals.onlinelibrary.wiley.com/doi/abs/10.1111/1365-2656.13965">dragonflies</a>. But don’t expect them to eat enough to keep all mosquitoes away.</p>
<p>Bats are often promoted as a good “biological control” options but studies have shown mosquitoes are <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0077183">more likely to be a snack food</a> for small bats, not an irresistible staple of their diet.</p>
<p>For garden ponds, frogs will eat a few adult mosquitoes but tadpoles of Australian frogs generally <a href="https://bioone.org/journals/journal-of-the-american-mosquito-control-association/volume-21/issue-4/8756-971X(2006)21%5b492%3aTOFCAF%5d2.0.CO%3b2/TADPOLES-OF-FOUR-COMMON-AUSTRALIAN-FROGS-ARE-NOT-EFFECTIVE-PREDATORS/10.2987/8756-971X(2006)21%5B492:TOFCAF%5D2.0.CO;2.short">don’t eat many mosquito “wrigglers”</a>. </p>
<p>Australian native fish <a href="https://pubmed.ncbi.nlm.nih.gov/15532929/">will readily eat mosquitoes</a> and may be useful for backyard ponds.</p>
<p>But not all fish are good. While “mosquitofish” (aka “plague minnow”) is distributed overseas to assist in mosquito control, <a href="https://meridian.allenpress.com/australian-zoologist/article/30/3/316/134508/Does-predation-by-the-fish-Gambusia-holbrooki">it’s a disaster for local wildlife</a> and, <a href="https://www.dpi.nsw.gov.au/fishing/aquatic-biosecurity/pests-diseases/freshwater-pests/finfish-species/gambusia">along with other exotic fish species</a>, should not be released into local waterways.</p>
<p><a href="https://link.springer.com/article/10.1007/s13157-019-01133-2">Healthier habitats promote fewer mosquitoes</a> so the best thing you can do is create habitats for the animals that eat mosquitoes. </p>
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Read more:
<a href="https://theconversation.com/you-can-leave-water-out-for-wildlife-without-attracting-mosquitoes-if-you-take-a-few-precautions-128631">You can leave water out for wildlife without attracting mosquitoes, if you take a few precautions</a>
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<h2>5. Avoid traps and other gadgets</h2>
<p>There are lots of devices purported to catch, kill, or repel mosquitoes from your garden. Some may catch a mosquito or two but they’re not very effective in knocking out big numbers.</p>
<p>“Bug zappers” with bright lights will collect lots of flying insects. It’s just that mosquitoes make up a very small proportion of collections. </p>
<p>Electrocuting devices, again, don’t seem to attract a lot of mosquitoes. </p>
<p>Devices that <a href="https://theconversation.com/the-buzz-from-your-smartphone-wont-stop-mosquito-bites-92611">emit high frequency sounds</a> won’t help either. </p>
<p>The best devices are typically those that are baited with carbon dioxide. These are a mainstay of state and territory <a href="https://www.health.nsw.gov.au/Infectious/mosquito-borne/Pages/surveillance.aspx">mosquito and arbovirus surveillance programs</a>. For a mosquito, the C0₂ tricks them into thinking the trap is a warm-blooded animal. The only problem is these can be expensive to run and don’t seem quite as effective for mosquito control <a href="https://bioone.org/journals/journal-of-the-american-mosquito-control-association/volume-22/issue-3/8756-971X(2006)22%5b490%3aTATTFA%5d2.0.CO%3b2/Traps-and-Trapping-Techniques-for-Adult-Mosquito-Control/10.2987/8756-971X(2006)22%5B490:TATTFA%5D2.0.CO;2.short">unless used in large numbers</a>. </p>
<h2>Yes, you’ll still need repellent</h2>
<p>Perhaps the best way to avoid mosquito bites is to pick an insect repellent <a href="https://www.phrp.com.au/issues/december-2016-volume-26-issue-5/a-review-of-recommendations-on-the-safe-and-effective-use-of-topical-mosquito-repellents/">recommended by health authorities</a> and <a href="https://theconversation.com/mozzies-biting-heres-how-to-choose-a-repellent-and-how-to-use-it-for-the-best-protection-150183">apply it</a> to ensure all exposed areas of skin are covered. These products and safe, affordable and effective.</p>
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Read more:
<a href="https://theconversation.com/mozzies-biting-heres-how-to-choose-a-repellent-and-how-to-use-it-for-the-best-protection-150183">Mozzies biting? Here's how to choose a repellent (and how to use it for the best protection)</a>
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<img src="https://counter.theconversation.com/content/212711/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Cameron Webb and the Department of Medical Entomology, NSW Health Pathology, have been engaged by a wide range of insect repellent and insecticide manufacturers to provide testing of products and provide expert advice on mosquito biology. Cameron has also received funding from local, state and federal agencies to undertake research into mosquito-borne disease surveillance and management.</span></em></p>Warm weather has arrived and that means our annual battle against mosquitoes is back on. Here are five ways to mosquito-proof your backyard that don’t rely on spraying insecticides.Cameron Webb, Clinical Associate Professor and Principal Hospital Scientist, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2117032023-08-18T13:16:43Z2023-08-18T13:16:43ZHow genetically modifying mosquitoes could strengthen the world’s war on malaria<figure><img src="https://images.theconversation.com/files/543058/original/file-20230816-19-7rtxgm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Genetic modification could make malaria-carrying mosquitoes harmless.</span> <span class="attribution"><span class="source">LeliaSpb/Getty Images</span></span></figcaption></figure><p>It’s been 126 years since British medical doctor Sir Ronald Ross <a href="https://www.nobelprize.org/prizes/medicine/1902/ross/facts/">discovered</a> that mosquitoes in the <em>Anopheles</em> family are primarily responsible for transmitting malaria parasites between vertebrate hosts. </p>
<p>Since his discovery, mosquitoes have been found to carry and transmit <a href="https://theconversation.com/mosquitoes-theres-malaria-plus-5-other-diseases-they-pass-on-to-humans-188856">many other diseases</a> that pose a major threat to public health. <a href="https://theconversation.com/mosquitoes-theres-malaria-plus-5-other-diseases-they-pass-on-to-humans-188856">Among them</a> are yellow fever, dengue and <a href="https://theconversation.com/understanding-zikas-silent-presence-in-africa-is-key-to-tackling-the-next-epidemic-80343">Zika</a>.</p>
<p>Currently, malaria is the most lethal mosquito-transmitted disease. The World Health Organization (WHO) <a href="https://www.who.int/news-room/fact-sheets/detail/malaria">reported</a> an estimated 247 million cases of malaria worldwide in 2021 and 619,000 deaths. <a href="https://www.who.int/news-room/fact-sheets/detail/malaria">Almost all cases and deaths</a> were in African countries.</p>
<p>Other diseases transmitted by mosquitoes are also a source of immense human suffering. It is <a href="https://www.worldmosquitoprogram.org/en/learn/mosquito-borne-diseases#:%7E:text=Common%20types%20of%20mosquito%2Dborne,chikungunya%2C%20yellow%20fever%20and%20Zika">estimated</a> that dengue infects about 390 million people annually. And thousands are affected by Zika, chikungunya and yellow fever. </p>
<p>Insects that transmit diseases to humans are known as vectors and the diseases they transmit are referred to as vector-borne diseases. These diseases are very difficult to control. They generally have complex life cycles, involving both the insect and the human host.</p>
<p>Conventional methods to control vector-borne diseases have targeted the vectors, focusing on reducing their opportunities to come into contact with humans. </p>
<p>This is <a href="https://www.who.int/teams/global-malaria-programme/prevention/vector-control#:%7E:text=Vector%20control%20is%20a%20highly,areas%20at%20risk%20of%20malaria">particularly true for malaria</a>. Insecticide-treated nets serve a dual function by acting as a physical barrier between the mosquito vector and humans, and exposing the mosquito to a lethal dose of insecticide when it lands on the net. In another common control method, mosquitoes are exposed to a lethal dose of insecticide through indoor residual spraying.</p>
<p>Both nets and indoor spraying have played <a href="https://endmalaria.org/sites/default/files/Kleinschmidt%20Immo_IRS%20and%20ITN%20combined%20effect.pdf#page=7">a major role</a> in reducing African countries’ malaria burden. But their sustained efficacy is under threat. Many vector populations have <a href="https://www.who.int/teams/global-malaria-programme/prevention/vector-control/insecticide-resistance">become resistant</a> to the insecticides used in these methods. They have also <a href="https://www.pbs.org/wgbh/nova/article/mosquito-behavioral-resistance/">changed their behaviours</a> to reduce their contact with those insecticides. </p>
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Read more:
<a href="https://theconversation.com/fresh-signs-of-mosquito-insecticide-resistance-in-south-africa-181618">Fresh signs of mosquito insecticide resistance in South Africa</a>
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<p>Scientists <a href="https://www.ivcc.com/research-development/insecticide-discovery-and-development/">are working</a> to address these issues. But other methods that don’t rely on insecticides are needed in the fight against mosquito-borne diseases. </p>
<p>That’s where genetic modification comes in. We are researchers focused on finding novel ways to advance malaria elimination efforts and are excited about recent advances in genomic research that make genetic modification a realistic option for malaria control in particular. As with other approaches to controlling or eventually eradicating the disease, this won’t be a complete solution. But it’s got the potential to strengthen the global fight against malaria.</p>
<h2>Genetic modification for malaria control</h2>
<p>Mosquitoes can be genetically modified through two different technologies. The first method, <a href="https://surface.syr.edu/cgi/viewcontent.cgi?article=1142&context=eli">paratransgenesis</a>, involves infecting mosquitoes with bacteria that prevent them from transmitting malaria. This doesn’t harm the mosquito. It is important not to eliminate or harm mosquitoes because they pollinate many plants and are <a href="https://www.reconnectwithnature.org/news-events/the-buzz/world-without-mosquitoes-not-as-easy-as-it-seems/">food</a> for animals like bats, birds and reptiles.</p>
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Read more:
<a href="https://theconversation.com/curious-kids-what-would-happen-if-all-the-mosquitoes-in-the-world-disappeared-175528">Curious Kids: What would happen if all the mosquitoes in the world disappeared?</a>
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<p>Scientists are excited about this method following the <a href="https://www.ft.com/content/c4db7776-e776-4717-bf9d-7792d5ff0ad0">recent discovery</a> of a bacterium that occurs naturally in mosquitoes’ guts and appears to prevent the malaria parasite from developing inside the mosquito.</p>
<p>The second method involves genetically modifying the mosquitoes themselves. This approach centres on <a href="https://www.synthego.com/blog/gene-drive-crispr">gene drives</a>: genetic systems that ensure genes of interest are inherited by all offspring in every generation. There are two types of gene drive. One aims to reduce the vector population size and is known as population suppression. The other aims to prevent the mosquito from transmitting malaria; it is known as population modification.</p>
<p>Gene drives focusing on population suppression have <a href="https://www.isaaa.org/kc/cropbiotechupdate/gdn/article/default.asp?ID=19494">shown great promise in laboratory studies</a>. They’ve yet to be tested in the field, though. </p>
<p>Population modification potentially has fewer environmental effects and is less prone to developing mutations. But it has proved more challenging to achieve and has not progressed as far as the suppression approach.</p>
<h2>Addressing scepticism</h2>
<p>It will be a while before this technology is routinely used by malaria control programmes. But preparation is under way. </p>
<p>Over the past decade, malaria control programmes have expressed a willingness to use genetic modification if and when such techniques are shown to be safe and acceptable to the affected communities. This has prompted the WHO <a href="https://www.who.int/news/item/19-05-2021-who-issues-new-guidance-for-research-on-genetically-modified-mosquitoes-to-fight-malaria-and-other-vector-borne-diseases">to provide guidance</a> on the use of genetically modified mosquitoes to control malaria and other vector-borne diseases.</p>
<p>In its guidance, the WHO acknowledges how crucial community engagement will be to the success of any future gene drive interventions.</p>
<p>This is important in an environment where there is <a href="https://theconversation.com/the-reasons-for-science-skepticism-can-be-complex-and-founded-on-real-concerns-171000">marked scepticism</a> about science, and particularly about genetically modified organisms (GMOs). In 2003, community resistance resulted in the rejection of genetically modified golden rice <a href="https://www.un.org/africarenewal/magazine/february-2003/controversy-rages-over-gm-food-aid#:%7E:text=Many%20Zambians%20believe%20that%20GMOs,in%20people%20with%20poor%20health.">in Zambia</a>, despite the country experiencing a pronounced food shortage. </p>
<p>More recently, there was backlash against the COVID-19 mRNA vaccines, which some people <a href="https://www.health.gov.au/our-work/covid-19-vaccines/is-it-true/is-it-true-can-covid-19-vaccines-alter-my-dna">suspected</a> of being capable of altering human DNA (it isn’t). </p>
<p>It is critical that the concerns of communities where genetically modified mosquitoes are to be released are addressed prior to any release. This will help promote acceptance and understanding of the new technology.</p>
<h2>Considerable investment</h2>
<p>However, community acceptance is not the only challenge. There is an urgent need for research on the relevant local malaria mosquito species so that the required genetically modified mosquitoes can be developed. Once the genetically modified lines are established, impact in the field must be demonstrated and systems established to ensure suitable numbers of mosquitoes can be reared and safely transported to the intervention sites. </p>
<p>All this requires considerable human resources and funding, suggesting that it will be some time before gene drive systems have real-world impact on malaria transmission.</p>
<p>Still, as the globe marks <a href="https://nationaltoday.com/world-mosquito-day/">World Mosquito Day</a> on 20 August, in honour of Sir Ronald Ross’s discovery almost 130 years ago, we believe there is reason for optimism: novel technologies like genetic modification have the potential to play a major role in the fight against malaria.</p><img src="https://counter.theconversation.com/content/211703/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Shüné Oliver receives funding from the National Research Foundation of South Africa, the South African Medical Research Council and the Female Academic Leadership Fellowship of the University of the Witwatersrand. She is affiliated to the Wits Research Institute for Malaria at the University of the Witwatersrand. </span></em></p><p class="fine-print"><em><span>Jaishree Raman receives funding from Bill and Melinda Gates Foundation, Global Fund, CHAI, South African Medical Research Council, South African Research Trust, National Research Foundation and the National Institute for Communicable Diseases. She is affiliated with the Wits Research Institute for Malaria, University of Witwatersrand and UP Institute for Sustainable Malaria Control, University of Pretoria.</span></em></p>Methods that don’t rely on insecticides are needed to bolster the fight against mosquito-borne diseases.Shüné Oliver, Medical scientist, National Institute for Communicable DiseasesJaishree Raman, Principal Medical Scientist and Head of Laboratory for Antimalarial Resistance Monitoring and Malaria Operational Research, National Institute for Communicable DiseasesLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2070882023-07-10T12:31:42Z2023-07-10T12:31:42ZNot all repellents are equal – here’s how to avoid mosquito bites this summer<figure><img src="https://images.theconversation.com/files/533800/original/file-20230623-17-1mi6af.jpg?ixlib=rb-1.1.0&rect=6%2C42%2C4019%2C2975&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A group of Anopheles mosquitoes taking a blood meal in an experiment conducted by the New Mexico State University Molecular Vector Physiology Lab. </span> <span class="attribution"><span class="source">Hansen MVP lab</span></span></figcaption></figure><p>Now that summer is in full swing, mosquitoes have come out across the United States. The use of mosquito repellents can protect both your health and sanity this summer.</p>
<p>While mosquitoes leave bothersome, itchy bites on your skin, they can also pose a serious and sometimes deadly risk to your health. When a mosquito bites you, it may transmit harmful pathogens that cause dangerous diseases like <a href="https://www.cdc.gov/parasites/malaria/index.html">malaria</a>, <a href="https://www.cdc.gov/dengue/">dengue fever</a>, <a href="https://www.cdc.gov/zika/">Zika</a> and <a href="https://www.cdc.gov/westnile/">West Nile</a>. </p>
<h2>Avoiding mosquito bites</h2>
<p>Mosquito females bite people to get vital nutrients from our blood. They then use these nutrients <a href="https://doi.org/10.3389/fphys.2014.00103">to make their eggs</a>. One single blood meal can give rise to about 100 mosquito eggs that hatch into wiggling larvae.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/532446/original/file-20230616-17-op8jl0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/532446/original/file-20230616-17-op8jl0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=448&fit=crop&dpr=1 600w, https://images.theconversation.com/files/532446/original/file-20230616-17-op8jl0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=448&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/532446/original/file-20230616-17-op8jl0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=448&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/532446/original/file-20230616-17-op8jl0.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=563&fit=crop&dpr=1 754w, https://images.theconversation.com/files/532446/original/file-20230616-17-op8jl0.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=563&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/532446/original/file-20230616-17-op8jl0.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=563&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"><em>Culex quinquefasciatus larvae</em> Mosquito larvae feed by filtering food from water. Getting rid of standing water can reduce mosquito habitats.</span>
<span class="attribution"><span class="source">Immo Hansen</span></span>
</figcaption>
</figure>
<p>There are several ways to <a href="https://www.cdc.gov/mosquitoes/mosquito-bites/prevent-mosquito-bites.html">avoid getting bitten by mosquitoes</a>, from wearing long, loose clothing and limiting time outside to placing screens over your windows and getting rid of standing water that mosquitoes might use to breed.</p>
<p>However, one of the best ways to protect yourself when you’re going to a place where hungry mosquitoes will be buzzing around is by using <a href="https://doi.org/10.1093/jisesa/iev125">mosquito repellents</a>. </p>
<p>Our team at the <a href="https://nmsu.edu/">New Mexico State University</a> <a href="https://www.hansenmvplab.com/">Molecular Vector Physiology Laboratory</a> has studied different types of mosquito repellents and their efficacy for over a decade. Here’s what you need to know to protect yourself this summer:</p>
<h2>All about repellents</h2>
<p>The use of mosquito repellents goes far back in history, certainly predating written historical accounts. <a href="https://doi.org/10.1201/9781420006650">Some of the oldest records</a> of the use of mosquito repellents date back to early Egyptian and Roman history. During this period, smoke from smudge fires was often used to repel mosquitoes. </p>
<p>Today, we have more options than our ancestors when it comes to choosing what type of mosquito repellent to use – <a href="https://www.nytimes.com/wirecutter/reviews/best-bug-repellent/">sprays and lotions</a>, candles, <a href="https://www.nytimes.com/wirecutter/reviews/mosquito-control-gear/">coils and vaporizers</a>, to name some. </p>
<p>These repellents interfere with a mosquito’s <a href="https://doi.org/10.1016/j.cub.2019.04.004">sense of smell, taste or both</a>. The repellent either blocks or overstimulates these senses. Scientists understand how certain repellents like DEET <a href="https://doi.org/10.1016/j.neuron.2010.07.006">work at the molecular level</a>, but for many of them, it is still unknown why exactly they repel mosquitoes.</p>
<h2>Testing repellents</h2>
<p>We used a variety of <a href="https://www.hansenmvplab.com/services">scientific laboratory experiments and field tests</a> to find out what works. For some products, testing was as simple as putting a volunteer’s treated arm into a cage with 25 mosquitoes and waiting for the first mosquito bite. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/532472/original/file-20230616-19-qwfotj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A researcher's arm covered in a protective sleeve, with part of their skin exposed while mosquitoes fly around." src="https://images.theconversation.com/files/532472/original/file-20230616-19-qwfotj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/532472/original/file-20230616-19-qwfotj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=336&fit=crop&dpr=1 600w, https://images.theconversation.com/files/532472/original/file-20230616-19-qwfotj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=336&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/532472/original/file-20230616-19-qwfotj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=336&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/532472/original/file-20230616-19-qwfotj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=422&fit=crop&dpr=1 754w, https://images.theconversation.com/files/532472/original/file-20230616-19-qwfotj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=422&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/532472/original/file-20230616-19-qwfotj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=422&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Arm-in-cage experimental setup.</span>
<span class="attribution"><span class="source">Keyla R. Salas</span></span>
</figcaption>
</figure>
<p>For others, like citronella candles, we used a <a href="https://www.krwg.org/krwg-news/2022-09-23/research-at-nmsu-looks-at-the-effectiveness-of-mosquito-repellents">slow-speed wind tunnel</a> and put a candle or device between a person and a cage of mosquitoes. Depending on the repellent efficacy of the device, mosquitoes either flew toward the person or away. Another experiment we conducted was the <a href="https://www.youtube.com/watch?v=38gVZgE39K8&t=23s">Y-tube choice assay</a> where mosquitoes chose to fly toward someone’s hand or, if repelled, fly toward the blank or empty option. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/38gVZgE39K8?wmode=transparent&start=23" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">This video from the YouTube channel Veritasium shows our team performing a Y-tube choice assay experiment.</span></figcaption>
</figure>
<h2>Mosquito repellents that don’t work</h2>
<p>Bracelets don’t work. Department stores and pharmacy chains sell hundreds of different varieties of bracelets. They are marketed as “mosquito repellent” bands, wristbands and watches, and their materials can vary from plastic to leather. Even if they are loaded with repellents, they can’t protect your whole body from mosquito bites. </p>
<p>Ultrasonic repellent devices don’t work. These come as electrical plug-ins, free-standing varieties or watchlike accessories that claim to emit a high-frequency sound that deters mosquitoes by mimicking bats. However, in <a href="https://doi.org/10.1111/j.1570-8703.2006.00463.x">scientific studies</a>, ultrasonic repellent devices fail to repel mosquitoes. In fact, when our lab <a href="https://doi.org/10.1093/jisesa/iew117">tested one of these devices</a>, we found a slight increase in mosquito attraction to the wearer. </p>
<p>Dietary supplements – vitamin B, garlic and so on – don’t work. No scientific evidence shows these supplements <a href="https://doi.org/10.1056/NEJMoa011699">protect people from mosquito bites</a>. </p>
<p>Light-based repellents don’t work. These devices come as colored light bulbs, and they don’t attract insects that fly toward white light. This approach works well on <a href="https://doi.org/10.1007/s13355-013-0219-x">moths, beetles and stinkbugs</a>, but not on mosquitoes. </p>
<h2>Mosquito repellents that work</h2>
<p>And here is our ranking of what does work, starting with the best repellent/active ingredient.</p>
<ol>
<li><p>DEET works. DEET, <a href="https://www.epa.gov/insect-repellents/deet">chemical name, N,N-diethyl-meta-toluamide</a>, was developed in the 1950s by the U.S. Army and is a <a href="https://doi.org/10.1081/CLT-120025348">well-established</a> mosquito repellent with a <a href="https://doi.org/10.1016/j.jaad.2007.10.005">long history of use</a>. The higher the percentage, the longer the protection time is – <a href="https://www.hindawi.com/journals/jpr/2015/361021/">up to six hours</a>.</p></li>
<li><p>Picaridin works. This synthetic repellent can protect for <a href="https://link.springer.com/article/10.1007/s00436-006-0450-2">up to six hours at a 20% concentration</a>. This repellent is a <a href="https://www.outdoors.org/resources/amc-outdoors/outdoor-resources/picaridin-vs-deet-which-is-the-best-insect-repellent/">promising alternative</a> for <a href="https://accpjournals.onlinelibrary.wiley.com/doi/full/10.1002/phar.1854">DEET</a>.</p></li>
<li><p>Oil of lemon eucalyptus, or OLE, works. OLE, with the active ingredient PMD, is a plant-based alternative to DEET and picaridin. Its repellent properties can last for <a href="https://academic.oup.com/jinsectscience/article/15/1/140/2583458">up to six hours</a>.</p></li>
<li><p>Other essential oils – some work, some not so much. We applied <a href="https://doi.org/10.1038/s41598-023-28820-9">20 different essential oils</a> in a 10% essential oil lotion mixture to volunteers’ skin. Here’s what we found: </p>
<p>Clove oil works. This oil, with the active ingredient eugenol, can protect from mosquito bites for over 90 minutes at a 10% concentration in lotion. Cinnamon oil works. This oil, with the active ingredients cinnamaldehyde and eugenol, can protect from mosquitoes for over 60 minutes at a 10% concentration in lotion. Geraniol and 2-PEP, or 2-phenylethyl propionate, work for about 60 minutes at a 10% concentration in lotion. Citronella oil works, just not so great. We found citronella oil at a 10% concentration only protected from mosquito bites for about 30 minutes. </p></li>
</ol>
<p><iframe id="vwJXh" class="tc-infographic-datawrapper" src="https://datawrapper.dwcdn.net/vwJXh/2/" height="400px" width="100%" style="border: none" frameborder="0"></iframe></p>
<p>If you are planning to mix your own plant-based mosquito repellent this summer, remember that essential oils are <a href="https://www.mdpi.com/2297-8739/10/2/128">complex mixtures of plant-made chemicals</a> that can cause skin irritations at high concentrations.</p>
<p>Based on our study, we recommend using repellents with the active ingredient DEET if you live in or are traveling to regions with a high risk of vector-borne disease transmission. However, plant-based repellents will work just fine to prevent nuisance mosquito bites in low-risk areas, as long as you reapply them as needed.</p><img src="https://counter.theconversation.com/content/207088/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Immo A. Hansen receives funding from the National Institute of Health. </span></em></p><p class="fine-print"><em><span>Hailey A. Luker receives funding from the National Institute of Health.</span></em></p>Two mosquito physiology experts explain which repellents work better than others and how to protect yourself this summer.Immo A. Hansen, Professor of Biology, New Mexico State UniversityHailey A. Luker, Ph.D. Student in Biology, New Mexico State UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2087262023-06-30T12:40:44Z2023-06-30T12:40:44ZLocally transmitted malaria in the US could be a harbinger of rising disease risk in a warming climate – 5 questions answered<figure><img src="https://images.theconversation.com/files/534730/original/file-20230629-15-k04fb9.jpg?ixlib=rb-1.1.0&rect=8%2C17%2C5879%2C3910&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Some evidence suggests that malaria mosquitoes are becoming resistant to insecticides.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/anopheles-maculipennis-royalty-free-image/522212584?phrase=malaria&adppopup=true">Paul Starosta/Stone via Getty Images</a></span></figcaption></figure><p><em>The Centers for Disease Control and Prevention reported on June 26, 2023, that five cases of <a href="https://emergency.cdc.gov/han/2023/han00494.asp">locally transmitted malaria had been identified</a> – four in Florida and one in Texas – since May 2023. These are the first cases of locally acquired mosquito-borne malaria in the U.S. since 2003.</em> </p>
<p><em>The Conversation spoke with <a href="https://stempel.fiu.edu/faculty-staff/profiles/chowdhury-rajiv.html">Dr. Rajiv Chowdhury</a>, a <a href="https://scholar.google.co.uk/citations?user=lmhOm1sAAAAJ&hl=en">global health expert</a> from Florida International University, about the significance of these cases and why they’re appearing now.</em></p>
<h2>1. What is malaria and how did these people become infected?</h2>
<p>Malaria is a serious and sometimes life-threatening disease caused by the bite of a female mosquito from the genus <em>Anopheles</em>, the vector <a href="https://www.niaid.nih.gov/diseases-conditions/malaria-parasite#">that transmits malaria</a>. </p>
<p>The most common symptoms are fever, chills, headaches, muscle aches and fatigue. These symptoms typically occur from 10 to 15 days after people are infected with the parasite. However, if untreated, more <a href="https://www.who.int/news-room/fact-sheets/detail/malaria">severe symptoms</a> may appear that include impaired consciousness, difficulty breathing, convulsions, abnormal bleeding and more, which can ultimately lead to death.</p>
<p>The five cases in Florida and Texas were caused by the <em>Plasmodium vivax</em> parasite, which is the most common malaria-causing parasite strain <a href="https://www.ncbi.nlm.nih.gov/books/NBK538333/">outside of the African continent</a>. All are believed to be locally acquired, which means they were not connected to any international travel. In addition, there is no evidence to suggest that the cases in the two states are related. <em>Plasmodium vivax</em> is the most globally widespread of all <em>Plasmodium</em> strains and can cause severe, often fatal, infections. </p>
<p>All five patients have <a href="https://www.floridahealth.gov/newsroom/2023/06/20230626-mosquito-borne-illnesses.pr.html">reportedly recovered</a>, and surveillance for additional cases is ongoing.</p>
<h2>2. Why might these cases be surfacing now?</h2>
<p>There could be several factors driving the emergence of locally acquired malaria.</p>
<p>For one, climate change is <a href="https://doi.org/10.1016/S0140-6736(17)31119-4">causing a shift in weather patterns</a>, some of which can worsen malaria conditions. A higher average surface temperature from global warming could lead to higher mosquito migration in areas that were <a href="https://doi.org/10.1016/S2542-5196(22)00039-0">previously uninhabitable by <em>Anopheles</em> mosquitoes</a>.</p>
<p>These higher temperatures could also <a href="https://www.un.org/en/chronicle/article/climate-change-and-malaria-complex-relationship">enhance the growth rate and transmissibility of the parasites</a> responsible for malaria. These include Plasmodium parasite variants such as <em>vivax</em>, <em>knowlesi</em> and <em>falciparum</em>.</p>
<p>The effects of climate change can also lead to <a href="https://doi.org/10.1186/s12936-021-03718-x">higher rainfall and sea level rise</a> in many places – both of which can result in more areas or open spaces with stagnant water that typically serve as effective breeding grounds for mosquitoes. </p>
<p>Given these changes in local conditions, more cases could occur in populations that were previously <a href="https://doi.org/10.1073/pnas.1302089111">“immunologically naïve” to malaria</a>. In other words, since these people have never been exposed to it, their immune systems are ill-equipped to fight it.</p>
<p>Furthermore, when people travel to countries or areas where climate-driven malaria cases are on the rise, there is a greater possibility of bringing those infections back to the U.S., where local mosquitoes could be exposed to the parasite in an infected person’s blood. </p>
<p>Lastly, due to misuse and overuse of common antimalarial medications, <a href="https://doi.org/10.1016/S2666-5247(21)00249-4">such as artemisinin</a>, antimicrobial resistance has become <a href="https://www.cdc.gov/malaria/malaria_worldwide/reduction/drug_resistance.html">a major problem in many regions</a> of the world. This drives up the number of drug-resistant cases, the severity of the illness and the possibility of larger outbreaks.</p>
<p>This is further complicated by emerging <a href="https://www.who.int/teams/global-malaria-programme/reports/world-malaria-report-2022">resistance to insecticides</a> among <em>Anopheles</em> mosquitoes.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/xzFQ8xEOtI8?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">When traveling overseas this summer, here’s what to remember.</span></figcaption>
</figure>
<h2>3. How can people help prevent malaria transmission?</h2>
<p>The CDC and the Florida Department of Health are urging people to protect themselves by using bug spray, avoiding areas where mosquitoes congregate and covering exposed skin.</p>
<p>Precautions also include what’s known as “<a href="https://www.floridahealth.gov/newsroom/2023/06/20230626-mosquito-borne-illnesses.pr.html">drain and cover</a>” – in other words, draining standing water to prevent mosquitoes from multiplying and using screens to prevent mosquitoes from entering through doors and windows. Health departments also note that it’s important to drain or discard containers that can collect rainwater, such as flower pots, old tires and buckets. </p>
<h2>4. What are the available malaria treatments?</h2>
<p>There are several medicines used to prevent and treat malaria. The choice of medication typically depends on the type of malaria, whether a malaria parasite is resistant to a medicine, the weight or age of the person infected with malaria and whether the person is pregnant. </p>
<p>Most malaria medicines are taken in pill form. The most common include combination therapy medicines that include a class of <a href="https://doi.org/10.1016%2Fj.tips.2008.07.004">semi-synthetic drugs called artemisinins</a>. These kill malaria parasites by damaging their proteins and are usually the most effective treatment against malaria. <a href="https://medlineplus.gov/druginfo/meds/a682318.html#">Chloroquine phosphate</a>, a medicine that has been used for decades to prevent and treat malaria, is now recommended for treatment of infection with <em>Plasmodium vivax</em>, but only in places where the parasite is still sensitive to this medicine. Lastly, there’s <a href="https://medlineplus.gov/druginfo/meds/a607037.html#">primaquine</a>, a class of antimalarial drugs typically added to complement another treatment to prevent any relapse of infection. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/Ouevc5xYfC0?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">With early diagnosis, malaria is very treatable.</span></figcaption>
</figure>
<h2>5. Are vaccines against malaria available?</h2>
<p>Nearly half of the <a href="https://www.who.int/news-room/fact-sheets/detail/malaria">global population is currently at risk</a> of malaria, with almost 250 million cases and 620,000 deaths worldwide, mostly affecting children. Therefore, in October 2021, the World Health Organization began <a href="https://theconversation.com/who-approved-a-malaria-vaccine-for-children-a-global-health-expert-explains-why-that-is-a-big-deal-169501">recommending the widespread use</a> of a malaria vaccine known as RTS,S/ASOI for children who live in moderate- to high-risk areas.</p>
<p>This is the first-ever <a href="https://www.who.int/news/item/06-10-2021-who-recommends-groundbreaking-malaria-vaccine-for-children-at-risk">vaccine for a human parasitic infection</a>. Trials show that the vaccine can <a href="https://doi.org/10.1016/S0140-6736(15)60721-8">significantly reduce malaria</a>, including severe malaria, among young children. </p>
<p>A group of scientists from the U.K. reported a <a href="https://doi.org/10.1016/S1473-3099(22)00442-X">modified version of this vaccine</a>, called R21, in September 2022. The early-phase clinical trial reported that the new vaccine is 80% effective at preventing disease in young children. However, real-world trials for this new candidate vaccine are still ongoing. </p>
<p>Other <a href="https://www.reuters.com/business/healthcare-pharmaceuticals/biontech-initiates-clinical-trial-mrna-based-malaria-vaccine-candidate-2022-12-23/#">vaccine candidates</a> are currently being developed by BioNTech, the company behind the Pfizer/BioNTech mRNA COVID-19 vaccine, and through <a href="https://www.forbes.com/sites/roberthart/2023/06/05/novavax-partners-with-gates-foundation-offshoot-in-efforts-to-develop-malaria-and-tb-shots/?sh=2354fd313d51">joint efforts</a> between Novavax and the Bill & Melinda Gates Medical Research Institute.</p>
<p>While new malaria vaccines will be a major boost for curbing malaria worldwide, it will be critical for health departments to continue emphasizing other preventive strategies, especially in newly affected areas like Florida and Texas.</p><img src="https://counter.theconversation.com/content/208726/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Rajiv Chowdhury does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>After recent cases in Florida and Texas, authorities are advising the public to drain standing water sources to keep mosquitoes from multiplying.Rajiv Chowdhury, Professor of Global Health, Florida International UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2080802023-06-23T13:39:45Z2023-06-23T13:39:45ZDo these seven things really stop mosquitoes biting you?<figure><img src="https://images.theconversation.com/files/533441/original/file-20230622-19-3p3f0e.jpg?ixlib=rb-1.1.0&rect=16%2C0%2C5447%2C3637&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/stressed-man-black-skin-scratching-itchy-2122741226">Pheelings media/Shutterstock</a></span></figcaption></figure><p>There’s one animal that ruins summer evenings: the mosquito. While mosquitoes don’t carry any diseases in the UK, their itchy bites are far from fun.</p>
<p>Everyone has a friend who gets covered in mosquito bites and a friend who doesn’t get a single one. That’s because mosquitoes use their sense of smell to find people to bite, and some people smell better to them. We can change how we smell using perfume, soaps, our diet and so on, but which changes can stop us from being bitten by mosquitoes?</p>
<h2>1. Soap brand</h2>
<p>As we all know, soaps affect how we smell, but people who use the same soap can end up smelling differently. <a href="https://www.cell.com/iscience/fulltext/S2589-0042(23)00744-7">A study published this year</a> found that, for some people, washing with Dove and Simple Truth soaps makes them more attractive to mosquitoes, whereas washing with Native soap repels them. But for other people, none of the soaps affect how attractive mosquitoes find them. </p>
<p>It might be worth hedging your bets and trying Native soap – but no guarantees.</p>
<h2>2. Bananas</h2>
<p>You might want to swap bananas for grapes this summer to avoid mosquito bites. <a href="https://www.mdpi.com/2075-4450/9/4/129">A US study</a> found that, for some people, mosquitoes were more attracted to the scent of their hands after they had eaten a banana. However, this pattern is not true for all fruits. The same methods were repeated using grapes, and there was no change in mosquito attraction to the volunteers after they had eaten them. </p>
<p>Choose your fruits wisely.</p>
<h2>3. Beer</h2>
<p><a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0009546">A 2010 study</a> measured how attractive mosquitoes found people before and after they drank either beer or water. After drinking beer, the volunteers’ body scent was more attractive to the mosquitoes. </p>
<p>But there was no change in how attractive mosquitoes found the volunteers after drinking water. So you might want to cut out the pints this summer – if you think it’s worth the sacrifice.</p>
<h2>4. Deodorant</h2>
<p><a href="https://www.nature.com/articles/srep27141">A study in Nature</a> found that a compound in deodorants (isopropyl tetradecanoate) repelled mosquitoes by preventing them from landing on the surface coated in deodorant. In fact, there was a 56% decrease in the number of mosquito landings. Imagine how many fewer bites that could lead to. </p>
<p>It’s even more important to remember to wear deodorant when exercising, as <a href="https://www.nature.com/articles/223859a0">another study in Nature</a> found that mosquitoes are more attracted to you if you’re sweaty.</p>
<p>It’s time to stock up on deodorants (your friends will thank you too).</p>
<h2>5. Garlic and vitamin B</h2>
<p>Many people eat garlic and take vitamin B supplements as a home remedy to repel mosquitoes. <a href="https://resjournals.onlinelibrary.wiley.com/doi/full/10.1111/j.0269-283X.2005.00544.x?casa_token=B8l3aJEndQkAAAAA%3A07qMmRgPH1VMVuqdjI3tkU2Wsk2LMGoUhJuBJYCXlxK7Ln7Mwof0DkxiCC0B075b81T5IRDeqDps">In a 2005 study</a>, participants were exposed to mosquitoes after consuming garlic or a placebo. The number of mosquito bites, alongside other measurements, was recorded, and the results provided no evidence that garlic repelled mosquitoes. </p>
<p>Similarly, another <a href="https://bioone.org/journals/Journal-of-the-American-Mosquito-Control-Association/volume-21/issue-2/8756-971X(2005)21%5b213:TVBAAH%5d2.0.CO;2/TESTING-VITAMIN-B-AS-A-HOME-REMEDY-AGAINST-MOSQUITOES/10.2987/8756-971X(2005)21%5b213:TVBAAH%5d2.0.CO;2.short">2005 study</a> found there was no effect of taking vitamin B supplements on the attractiveness of skin scent to mosquitoes. </p>
<p>Don’t bother with these home remedies. </p>
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<img alt="Garlic cloves" src="https://images.theconversation.com/files/533487/original/file-20230622-27-ld29gz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/533487/original/file-20230622-27-ld29gz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=401&fit=crop&dpr=1 600w, https://images.theconversation.com/files/533487/original/file-20230622-27-ld29gz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=401&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/533487/original/file-20230622-27-ld29gz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=401&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/533487/original/file-20230622-27-ld29gz.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=504&fit=crop&dpr=1 754w, https://images.theconversation.com/files/533487/original/file-20230622-27-ld29gz.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=504&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/533487/original/file-20230622-27-ld29gz.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=504&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Garlic might ward off vampires, but it’s less successful against other blood-sucking pests.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/organic-white-garlic-on-black-slate-1882991158">Jorge Lebron/Shutterstock</a></span>
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<h2>6. Deet repellent</h2>
<p><a href="https://en.wikipedia.org/wiki/DEET">Deet</a> is a chemical found in many insect repellents and can be used on bare skin. It doesn’t smell too good (to us and to mosquitoes) and can feel a little oily, but insect repellents containing Deet offer the <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9458079/#:%7E:text=Repellency%20Bioassay,from%201%20to%205.63%20h.">longest protection against mosquito bites</a>, compared with other repellents. </p>
<p>You might want to pop out and get some Deet – it’s relatively cheap and widely available. </p>
<h2>7. Treating clothes with insecticide</h2>
<p>If you don’t like the idea of putting repellent directly on your skin, you can spray your clothes with insecticide, such as <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4596613/#R5">permethrin</a>). This is an <a href="https://resjournals.onlinelibrary.wiley.com/doi/full/10.1111/mve.12068">effective way</a> to prevent mosquitoes from biting skin covered by the treated clothing, and is a technique used by the military. Mosquitoes often bite through untreated clothes, so this is worth doing. </p>
<p>Get out your favourite clothes and start spraying.</p>
<p>Have you tried all of these things and are still getting bitten to shreds? That’s because your <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4406498/">genetics</a> also influence how you smell, and therefore how attractive you are to mosquitoes. Bad luck!</p><img src="https://counter.theconversation.com/content/208080/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Maisie Vollans is supported by a BBSRC studentship and a scholarship from The Pirbright Institute. </span></em></p>An expert on mosquito ecology provides top tips to avoid being bitten by these pesky insects.Maisie Vollans, PhD Candidate, Mosquito Ecology, University of OxfordLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2041482023-04-24T12:04:29Z2023-04-24T12:04:29ZNigeria has Africa’s highest malaria death rate - progress is being made, but it’s not enough<figure><img src="https://images.theconversation.com/files/522576/original/file-20230424-1209-sj0dw5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Lagos residents use art to draw attention to the gaps in the prevention and treatment of malaria. According to UNICEF, over 1,000 children under the age of 5 catch malaria every day. </span> <span class="attribution"><span class="source">Pius Utomi Ekpei/AFP via Getty Images</span></span></figcaption></figure><p><em><a href="https://www.who.int/news-room/fact-sheets/detail/malaria">Malaria</a> is a major public health problem and can be life-threatening. The disease, mostly found in tropical countries, is transmitted to humans by the female Anopheles mosquito. Nearly half of the world’s population is at risk of the disease. <a href="https://www.who.int/news-room/fact-sheets/detail/malaria">In 2021</a>, for instance, around 247 million cases of malaria were reported and <a href="https://www.who.int/news-room/fact-sheets/detail/malaria">about 619,000</a> people died. <a href="https://www.who.int/news-room/fact-sheets/detail/malaria">Four African countries</a> accounted for just over half of all malaria deaths worldwide: Nigeria (31.3%), the Democratic Republic of the Congo (12.6%), Tanzania (4.1%) and Niger (3.9%).</em></p>
<p><em><a href="https://msh.org/people/dr-olugbenga-a-mokuolu/">Professor Olugbenga A. Mokuolu </a>currently oversees all malaria work in Nigeria for Management Sciences for Health, a global health advisory organisation. He’s also the former technical director to the National Malaria Elimination Programme in Nigeria. Molecular parasitology Professor, Segun Isaac Oyedeji, spoke to him about Nigeria’s malaria burden.</em></p>
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<p><strong>Segun Oyedeji:</strong> Nigeria has a high malaria burden. How did it get here?</p>
<p><strong>Olugbenga Mokuolu:</strong> It’s a combination of many things.</p>
<p>The existence of malaria anywhere is an interaction between the environment and the organism responsible for the disease, the mosquito. When you look at an environment, you’re looking at a variety of natural factors – such as temperature, humidity and rainfall – and man-made factors, such as drainage systems. This is because certain conditions allow mosquitoes to thrive – specifically moisture-rich environments. Mosquitoes <a href="https://theconversation.com/heavy-rains-put-kenya-at-risk-of-mosquito-borne-diseases-130076">breed by laying</a> their eggs in stagnant water. </p>
<p>Nigeria’s environment is a favourable one in which mosquitoes – the malaria vector – can thrive. </p>
<p>In terms of environmental management, Nigeria leaves a lot to be desired. The country has open refuse sites, blocked drainage systems, and – because people lack piped water – they store water at home in containers. These all provide <a href="https://www.cdc.gov/mosquitoes/about/where-mosquitoes-live.html">ideal sites</a> for mosquitoes to breed.</p>
<p>In terms of humidity, Nigeria has <a href="https://www.intechopen.com/chapters/65196">vegetation</a> that favours the reproductive stages of the parasite in the mosquito. <a href="https://pubmed.ncbi.nlm.nih.gov/14596287/#:%7E:text=The%20primary%20effect%20of%20increasing,at%20extraordinarily%20low%20vector%20densities.">Altitude also plays a role</a>. And, in most of Nigeria, the altitude allows the mosquito to fly around without much difficulty. Only the <a href="https://www.nigeriagalleria.com/Nigeria/States_Nigeria/Taraba/Mambilla-Plateau-Taraba.html">Mambilla Plateau</a> is considered relatively malaria free in Nigeria. It has an altitude that is above 5000 feet which makes it difficult for mosquitoes to inhabit. </p>
<p>In addition to this, Nigeria has a large population which makes malaria transmission much easier. Large populations mean more people tend to live closer together, which makes it easier for the mosquito vector to quickly find a contact for transmission of the malaria parasite. In addition, a large population puts more pressure on sanitation services, leading to more mosquito breeding sites. </p>
<p>That’s not to say no progress has been made. The country’s interventions have not been a failure altogether. My organisation is supporting Nigeria to provide preventive chemotherapy for malaria. We have reached over 25 million children under five in our intervention cycles. This is shown to have significant contribution to reduction in mortality. But we are not yet where we are supposed to be.</p>
<p><strong>Segun Oyedeji:</strong> Children are disproportionately affected. What can be done?</p>
<p><strong>Olugbenga Mokuolu:</strong> The Nigerian government and its partners have singled out children as the focus of most interventions. In addition, we need health system strengthening to address the gaps in access particularly at communities. </p>
<p>The Nigerian National Agency for Food and Drug Administration And Control <a href="https://www.nafdac.gov.ng/press-briefing-by-prof-mojisola-christianah-adeyeye-director-general-national-agency-for-food-and-drug-administration-and-control-nafdac-on-the-regulatory-approval-of-r21-malaria-vaccine-by-nafdac/">recently approved</a> the R21 malaria vaccine for use. </p>
<p>Hopefully when the R21 vaccine becomes available it will reduce new cases or the impact of cases. It is unclear when the vaccine may be rolled out in Nigeria. </p>
<p>A recent study shows that the <a href="https://www.ox.ac.uk/news/2023-04-13-r21matrix-m-malaria-vaccine-developed-university-oxford-receives-regulatory#:%7E:text=This%20followed%202021%20results%20from,and%20a%20reassuring%20safety%20profile.">R21 vaccine has some efficacy</a>. This vaccines has shown most effective when administered to children from five months to 36 months old. It is 77% effective in preventing infection and reduces the occurrence of severe malaria. Reducing the frequency of severe malaria reduces the burden of malaria mortality by extension. </p>
<p>The vaccines won’t be used on their own. They will be used as adjuncts to existing tools for fighting malaria such as preventative treatment and the distribution of bed nets.</p>
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Read more:
<a href="https://theconversation.com/what-nigeria-must-do-to-eliminate-malaria-three-researchers-offer-insights-159460">What Nigeria must do to eliminate malaria: three researchers offer insights</a>
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<p><strong>Segun Oyedeji:</strong> How can Nigeria reduce its malaria burden? </p>
<p><strong>Olugbenga Mokuolu:</strong> New cases of malaria can only be curbed by environmental measures, including the use of insecticide nets and personal protection. I know the vaccines aren’t 100% effective, but surely they will offer additional prevention. </p>
<p>But Nigeria needs to step up its game. The current <a href="https://drive.google.com/file/d/10da1qdiUbqxcZZHGa7uZxStnyFn9nFo-/view?pli=1">National Malaria Strategic Plan 2021 to 2025</a> is based on a well researched model. It is no longer business as usual. The plan clearly shows that if we don’t do more, malaria will keep rising. </p>
<p>But we are actually doing a lot.</p>
<p>Take the bed nets. These are being distributed on an almost regular basis to eligible states. Even COVID-19 didn’t stop the distribution. Now because of the size of Nigeria’s population, bed nets are distributed in what we call mass roll out campaigns with each state doing its own campaign. The improvement in malaria control that we have seen the last five to seven years is based on the intensity of interventions in two thirds of our states. </p>
<p>But Nigeria has gone further to almost be a global example, in how to implement <a href="https://www.who.int/teams/global-malaria-programme/prevention/preventive-chemotherapies">preventive chemotherapy</a>. We have 21 states out of 36 states where we reached over 25 million under five children in each cycle of intervention. We have four cycles in the year and this has contributed to reduction in mortality. </p>
<p>But we could do more. </p>
<p>Malaria isn’t going to be reduced significantly unless Nigeria intensifies development. Development plays a <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7856737/">major role</a> in reducing the burden. </p>
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Read more:
<a href="https://theconversation.com/ending-malaria-in-africa-needs-to-focus-on-poverty-quick-fixes-wont-cut-it-169205">Ending malaria in Africa needs to focus on poverty: quick fixes won't cut it</a>
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<p>Also, infusion of funds and not just from the government. There is also public-private partnership for drug manufacturers. The government should give them a protected market and negotiate good prices. Let the manufacturers take over distribution using their own market principles in a manner that will be affordable to many people.</p>
<p>We need to look at new initiatives and also position ourselves in the vaccine game with respect to malaria. </p>
<p><strong>Segun Oyedeji:</strong> How can the international community – donors and aid agencies – best support Nigeria? </p>
<p><strong>Olugbenga Mokuolu:</strong> International partners are supporting the country in many ways. Largely the support is in funding and technical areas. Going forward, countries like Nigeria will need stronger support for consolidating current gains, new tools, health system strengthening, scaling up access to vaccine and local manufacturing or production of malaria intervention commodities.</p><img src="https://counter.theconversation.com/content/204148/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Segun Isaac Oyedeji receives funding from Deutscher Akademischer Austausch Dienst (DAAD), Tertiary Education Trust Fund (TETFUND).</span></em></p>Nigeria must do more to reduce its high malaria burden.Segun Isaac Oyedeji, Professor in Molecular Parasitology and Genetics, Federal University, Oye EkitiLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2041972023-04-24T07:40:10Z2023-04-24T07:40:10ZHope is on the horizon for a malaria-free Africa<figure><img src="https://images.theconversation.com/files/522551/original/file-20230424-22-80rbgd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A factory producing insecticidal bed nets in Arusha, Tanzania.
</span> <span class="attribution"><span class="source">Photo by Charles Ommanney/Getty Images</span></span></figcaption></figure><p>Sub-Saharan Africa is <a href="https://www.who.int/news-room/fact-sheets/detail/malaria">disproportionally affected by malaria</a>. The region accounts for 95% of the world’s malaria cases. The disease kills an African child every <a href="https://data.unicef.org/topic/child-health/malaria/">60 seconds</a>. </p>
<p>These figures are alarming. But malaria is preventable and treatable. </p>
<p>The progress made between 2000 and 2015 is proof of what can be achieved. Support from global donors helped <a href="https://apps.who.int/iris/bitstream/handle/10665/205224/WHO_HTM_GMP_2016.2_eng.pdf#page=9">drive down malaria deaths</a> among children under five from 723,000 to 306,000. Most of the deaths prevented were in sub-Saharan Africa. Fifty-five of the 106 malaria-endemic countries showed a 75% decrease in new malaria cases by <a href="https://www.who.int/news/item/09-12-2015-new-report-signals-country-progress-in-the-path-to-malaria-elimination">2015 compared to 2000</a>. </p>
<p>But <a href="https://reliefweb.int/report/world/world-malaria-report-2017">in 2016</a>, the global malaria response plateaued. In some regions it even backtracked. Malaria <a href="https://www.devex.com/news/world-is-badly-off-track-in-reaching-malaria-goals-102222">cases and deaths increased</a> as national malaria control programmes competed with other health challenges. </p>
<p>The World Health Organization (WHO) and other partners issued urgent calls to address the challenges national programmes were facing. But the gap in funding and technical capacity widened. Malaria control efforts in Africa remained woefully <a href="https://www.afro.who.int/news/getting-malaria-prevention-back-track#:%7E:text=We%20are%20off%20the%20track,indicating%20that%20we%20are%20stagnating">off-track</a> to meeting 2030 elimination targets. </p>
<p>And then the COVID-19 pandemic hit. </p>
<p>At the start of the pandemic, there were <a href="https://www.reuters.com/article/us-africa-malaria-idUSKCN22529Q">dire warnings</a> of catastrophic disruptions to routine malaria services. These were expected to lead to a doubling of malaria deaths in Africa. </p>
<p>There were disruptions. But national malaria control programmes have shown impressive resilience over the past three years. Innovative actions saw malaria deaths increase by only <a href="https://data.unicef.org/topic/child-health/malaria/">10%</a> between 2019 and 2020. Malaria deaths didn’t double, and have <a href="https://www.who.int/news/item/08-12-2022-despite-continued-impact-of-covid-19--malaria-cases-and-deaths-remained-stable-in-2021">remained stable in 2021</a>.</p>
<p>Now, the battle to eliminate and eventually eradicate malaria has become even more challenging. The challenges include the impact of climate change on the distribution of malaria-carrying mosquitoes; the invasion and rapid spread of new mosquito species; as well as emerging drug-resistant malaria parasites and insecticide-resistant mosquitoes. </p>
<p>However, there is hope on the horizon. After decades of intense research, two new malaria vaccines have come to market. And researchers are developing new treatments and experimenting with different drug combinations. It may not happen by 2030, but malaria can be <a href="https://healthpolicy-watch.news/malaria-eradication-feasible-by-2050-says-new-lancet-commission-report/">eradicated</a>. </p>
<h2>History</h2>
<p>In 2000, the United Nations launched the <a href="https://research.un.org/en/docs/dev/2000-2015">millennium development goals</a>. One of the goals was to <a href="https://documents-dds-ny.un.org/doc/UNDOC/GEN/N00/559/51/PDF/N0055951.pdf?OpenElement">reduce the malaria burden</a> by 75% by 2015. This catalysed significant investments, particularly in sub-Saharan Africa. Between 2000 and 2015, international donor funding primarily from the <a href="https://www.theglobalfund.org/en/">Global Fund to Fight AIDS, Tuberculosis and Malaria</a> and the American government-led <a href="https://www.pmi.gov/">President’s Malaria Initiative</a>, enabled national malaria control programmes in Africa to replace failing interventions with more effective ones. </p>
<p>By <a href="https://www.who.int/teams/global-malaria-programme/reports/world-malaria-report-2016">2015</a>, over 150 million insecticide-treated bednets; 179 million malaria rapid diagnostic tests; and 153 million doses of the malaria treatment recommended by the WHO – artemisinin-based combination therapies (ACTs) – had been distributed across Africa. </p>
<p>Encouraged by the progress in rolling back malaria, the WHO launched the <a href="https://www.who.int/publications/i/item/9789241564991">Global Technical Strategy for Malaria</a>. This strategy provided malaria-endemic countries with a roadmap for reducing malaria transmission. The ultimate aim was to have a world free of malaria by 2030. </p>
<p>Unfortunately, the release of this strategy coincided with a levelling off in domestic and international funding, which led to an uptick in malaria cases.</p>
<p>In <a href="https://cdn.who.int/media/docs/default-source/Documents/world-malaria-report-2017.pdf?sfvrsn=8b7b573a_0">2016</a>, there were 216 million cases – five million more than in 2015. Ninety per cent of the new cases were in Africa where funding had dropped to less than <a href="https://reliefweb.int/report/world/world-malaria-report-2017">42%</a> of what the continent required for effective malaria control. </p>
<h2>Setbacks</h2>
<p>Now the global malaria response faces new challenges. </p>
<p>Climate change <a href="https://www.news-medical.net/health/The-Effect-of-Climate-Change-on-Malaria.aspx">experts predict</a> that as the Earth warms up, malaria will spread into malaria-free areas. The malaria mosquito and parasite will develop faster. And that malaria transmission rates in areas where the disease is currently will increase. In addition, environmental changes linked to human activities, such as deforestation, are also likely to change the distribution of mosquitoes and the diseases they carry.</p>
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Read more:
<a href="https://theconversation.com/how-higher-temperatures-and-pollution-are-affecting-mosquitoes-114768">How higher temperatures and pollution are affecting mosquitoes</a>
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<p>The recent <a href="https://reliefweb.int/report/world/vector-alert-anopheles-stephensi-invasion-and-spread-africa-and-sri-lanka">invasion and rapid spread</a> of the Asian malaria vector, <em>Anopheles stephensi</em>, through the Horn of Africa and as far west as Nigeria, may be an example of this. It has been identified as a threat to malaria elimination efforts in Africa. This mosquito species is <a href="http://www.mesamalaria.org/mesa-track/deep-dives/anopheles-stephensi">extremely difficult to control</a>. It thrives in urban areas, bites both in and outdoors, feeds on animals and humans, and is resistant to several insecticide classes. Acutely aware of the threat that this mosquito poses to malaria control in Africa, the WHO released an <a href="https://www.who.int/news/item/29-09-2022-who-launches-new-initiative-to-stop-the-spread-of-invasive-malaria-vector-in-africa">initiative</a> to slow the spread of this vector into the rest of Africa.</p>
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Read more:
<a href="https://theconversation.com/a-new-invasive-mosquito-has-been-found-in-kenya-what-this-means-for-malaria-control-200753">A new invasive mosquito has been found in Kenya – what this means for malaria control</a>
</strong>
</em>
</p>
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<p>Not to be outdone, the malaria parasite has also thrown a few curve balls into the mix. <em>Plasmodium falciparum</em> is the deadliest and most prevalent human malaria parasite in Africa. It has <a href="https://apps.who.int/iris/bitstream/handle/10665/325528/WHO-CDS-GMP-2019.02-eng.pdf">mutated</a> and can go undetected by the most widely used point-of-care diagnostic tool in rural malaria endemic regions. This leaves malaria-infected individuals at risk of developing severe illness, and still capable of transmitting malaria. In addition, African malaria parasites from Eritrea, Rwanda and Uganda have become resistant to the artemisinin part of ACTs. ACTs are the only class of effective antimalarial currently available. The WHO has developed a <a href="https://www.who.int/news/item/18-11-2022-tackling-emerging-antimalarial-drug-resistance-in-africa">strategy</a> for tackling emerging resistance in Africa.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/some-malaria-parasites-are-evading-detection-tests-causing-an-urgent-threat-to-public-health-177258">Some malaria parasites are evading detection tests, causing an urgent threat to public health</a>
</strong>
</em>
</p>
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<h2>Way ahead</h2>
<p>In 2021, the WHO took the bold step of approving the use of the RTS,S malaria vaccine in high-burden countries, despite its very modest efficacy of less than <a href="https://www.malariavaccine.org/malaria-and-vaccines/rtss">40%</a>. </p>
<p>A newer version of the RTS,S vaccine, the R21 vaccine produced by Oxford University’s Jenner Institute, has shown much high efficacy in a Phase III trial. This has prompted <a href="https://www.theguardian.com/global-development/2023/apr/13/ghana-is-first-country-to-approve-oxford-r21-malaria-vaccine">Ghana</a> and <a href="https://punchng.com/breaking-nigeria-becomes-second-country-to-approve-r21-malaria-vaccine/">Nigeria</a> to approve its use this month without pre-approval from the WHO.</p>
<p>Researchers are developing newer, more effective <a href="https://www.radboudumc.nl/en/news-items/2022/new-malaria-drug-is-ready-for-testing-in-humans">antimalarials</a>. Others are investigating using <a href="https://www.eurekalert.org/news-releases/521924">different combinations</a> of existing drug and <a href="https://www.nih.gov/news-events/nih-research-matters/antibody-treatment-protects-adults-against-malaria">antibodies</a> to effectively treat malaria. </p>
<p>Newer, more effective insecticide-treated nets are being <a href="https://reliefweb.int/report/world/who-publishes-recommendations-two-new-types-insecticide-treated-nets">rolled out</a>. And <a href="https://www.who.int/initiatives/genomic-surveillance-strategy">genomic surveillance</a> is a new tool in the malaria elimination toolbox to assist with evidence-based decision-making.</p><img src="https://counter.theconversation.com/content/204197/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jaishree Raman is affiliated with the National Institute for Communicable Diseases, the Wits Research Institute for Malaria and UP Institute for Sustainable Malaria Control. She receives funding from the Bill and Melinda Gates Foundation, the Global Fund, Clinton Health Access Initiative, the South African Medical Research Council, the South African Research Trust, the National Research Foundation and the National Institute for Communicable Diseases.</span></em></p>There have been disruptions. But national malaria control programmes have shown impressive resilience.Jaishree Raman, Principal Medical Scientist and Head of Laboratory for Antimalarial Resistance Monitoring and Malaria Operational Research, National Institute for Communicable DiseasesLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1978942023-01-17T05:07:23Z2023-01-17T05:07:23ZMurray Valley encephalitis has been detected in mozzies in NSW and Victoria. Here’s what you need to know<p>Where there’s water, you’ll find mosquitoes – including some that transmit viruses that can make us seriously ill. </p>
<p>Authorities have been on alert after an outbreak of Japanese encephalitis last summer which resulted in <a href="https://www.health.gov.au/health-alerts/japanese-encephalitis-virus-jev/japanese-encephalitis-virus-jev?language=en">45 human cases and seven deaths</a>. Favourable conditions for mosquitoes <a href="https://theconversation.com/a-wet-spring-and-summer-means-more-mosquitoes-but-now-weve-got-japanese-encephalitis-virus-to-worry-about-too-191510">continued</a>. </p>
<p>Now, we’ve seen the return of another pathogen to southeastern Australia: Murray Valley encephalitis virus. Mosquitoes carrying the virus have been detected in <a href="https://www.health.nsw.gov.au/news/Pages/20230111_00.aspx">New South Wales</a> and northern <a href="https://www.health.vic.gov.au/health-alerts/murray-valley-encephalitis-virus-detected-in-victoria">Victoria</a>.</p>
<p>While Murray Valley encephalitis is endemic in Northern Australia, meaning it is always present in mosquitoes, it’s not often detected in southeastern Australia. No human cases have yet been reported in the southern states, but past outbreaks after floods show we need to be cautious.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/how-to-mozzie-proof-your-property-after-a-flood-and-cut-your-risk-of-mosquito-borne-disease-178299">How to mozzie-proof your property after a flood and cut your risk of mosquito-borne disease</a>
</strong>
</em>
</p>
<hr>
<h2>What is Murray Valley encephalitis virus?</h2>
<p><a href="https://www.health.nsw.gov.au/Infectious/factsheets/Pages/murray-valley-encephalitis.aspx">Murray Valley encephalitis virus</a> is a member of the <a href="https://theconversation.com/5-virus-families-that-could-cause-the-next-pandemic-according-to-the-experts-189622">Flavivirus family</a>, which includes Japanese encephalitis, <a href="https://www.who.int/news-room/fact-sheets/detail/dengue-and-severe-dengue">dengue</a>, <a href="https://www.who.int/news-room/fact-sheets/detail/yellow-fever">yellow fever</a> and <a href="https://www.cdc.gov/westnile/index.html">West Nile</a> viruses. </p>
<p>Murray Valley encephalitis causes similar symptoms to <a href="https://www.health.nsw.gov.au/Infectious/factsheets/Pages/japanese_encephalitis.aspx">Japanese encephalitis</a> virus. <a href="https://theconversation.com/japanese-encephalitis-virus-can-cause-deadly-brain-swelling-but-in-less-than-1-of-cases-178985">Encephalitis</a> means inflammation, or swelling, of the brain.</p>
<p>Only a small proportion of people infected, <a href="https://www.mja.com.au/journal/2012/196/5/murray-valley-encephalitis-review-clinical-features-diagnosis-and-treatment">perhaps as few as one in 1,000</a>, will develop symptoms. These include fever, headache and vomiting, as well as neurological problems resulting in confusion, dizziness, or loss of consciousness.</p>
<p>The disease, like that caused by Japanese encephalitis virus, is fatal in <a href="https://www.mja.com.au/journal/2012/196/5/murray-valley-encephalitis-review-clinical-features-diagnosis-and-treatment">up to 30%</a> of those who get symptoms. </p>
<p>People who survive may have permanent neurological complications that require life-long medical care. Only <a href="https://www.mja.com.au/journal/2012/196/5/murray-valley-encephalitis-review-clinical-features-diagnosis-and-treatment">around 40%</a> of those experiencing severe symptoms recover completely.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/a-wet-spring-and-summer-means-more-mosquitoes-but-now-weve-got-japanese-encephalitis-virus-to-worry-about-too-191510">A wet spring and summer means more mosquitoes but now we've got Japanese encephalitis virus to worry about too</a>
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</em>
</p>
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<h2>How does it spread?</h2>
<p>Waterbirds such as herons and egrets are the <a href="https://www.liebertpub.com/doi/abs/10.1089/vbz.2008.0040">natural hosts</a> of the virus. Mosquitoes pick up the virus as they feed on the blood of birds, and then pass it on to people when the mosquitoes bite again.</p>
<p>The key mosquito <a href="https://onlinelibrary.wiley.com/doi/abs/10.1038/icb.1984.61">driving spread of the virus</a> is <em>Culex annulirostris</em>. It thrives in freshwater habitats and <a href="https://europepmc.org/article/med/1474387">travels many kilometres</a> from local wetlands.</p>
<p>The virus circulates between mosquitoes and waterbirds during the wet season in <a href="https://www.healthywa.wa.gov.au/Articles/J_M/Murray-Valley-encephalitis-and-Kunjin-viruses">northern Australia</a>, particularly in the <a href="https://pubmed.ncbi.nlm.nih.gov/14628944/">Kimberley region</a>. </p>
<p>After flooding, the virus makes its way into southeastern Australia from northern regions of the country. <a href="https://www.dcceew.gov.au/water/cewo/media-release/waterbird-resurgence-murray-darling-basin">Waterbirds travel to newly flooded areas</a> for favourable feeding and breeding conditions. </p>
<p>With flooding continuing in southeastern Australia, as well as <a href="https://www.abc.net.au/news/2023-01-14/bom-warning-forecast-weather-flooding-rainfall-north-central-qld/101855568">Queensland</a> and <a href="https://theconversation.com/disastrous-floods-in-wa-why-were-we-not-prepared-197407">Western Australia</a>, mosquito numbers are expected to remain high in many regions of Australia for months ahead. More mosquitoes and more waterbirds increase the likelihood of infection in people.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/504686/original/file-20230116-20-ma9aul.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/504686/original/file-20230116-20-ma9aul.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/504686/original/file-20230116-20-ma9aul.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/504686/original/file-20230116-20-ma9aul.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/504686/original/file-20230116-20-ma9aul.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/504686/original/file-20230116-20-ma9aul.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/504686/original/file-20230116-20-ma9aul.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The Nankeen Night Heron is a host of Murray Valley encephalitis virus.</span>
<span class="attribution"><span class="source">Paul Balfe/Flickr</span></span>
</figcaption>
</figure>
<h2>What happened in past outbreaks?</h2>
<p>The virus was first isolated in 1951 from patients who died from encephalitis in the Murray Valley. The outbreak included <a href="https://link.springer.com/article/10.1007/BF01321074">45 reported cases, including 19 deaths</a>.</p>
<p>But that wasn’t the first or last outbreak. There is evidence the virus was causing human disease in the early 1900s and at the time was known as “<a href="https://www.sciencedirect.com/science/article/pii/037811359500074K">Australian X disease</a>”.</p>
<p>The most significant outbreak occurred in 1974 with <a href="https://link.springer.com/article/10.1007/BF01321074">58 cases reported including 13 fatalities</a>. Seasonal agricultural workers became <a href="https://trove.nla.gov.au/newspaper/article/110760785?searchTerm=Murray%20valley%20encephalitis%20virus">reluctant to travel</a> to the regions impacted by the virus.</p>
<p>The virus didn’t disappear after 1974. It has been sporadically detected in humans, mosquitoes, or other animals, most commonly in <a href="https://academic.oup.com/trstmh/article/111/6/248/4554990#113640420">northern</a> and <a href="https://pubmed.ncbi.nlm.nih.gov/11950201/">central</a> Australia.</p>
<p>The largest outbreak since 1974 in southeastern Australia was in 2011, with a total of <a href="https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0002656">17 cases reported including three deaths</a>. </p>
<p>The major trigger for previous outbreaks has always been above average rainfall.</p>
<h2>What can we do about it?</h2>
<p><a href="https://www.health.nsw.gov.au/infectious/jev/pages/vaccination.aspx">Unlike Japanese encephalitis</a>, there is no vaccine for Murray Valley encephalitis. </p>
<p>Preventing mosquito bites is critical to stop infection. The <a href="https://theconversation.com/mozzies-biting-heres-how-to-choose-a-repellent-and-how-to-use-it-for-the-best-protection-150183">steps you take to stop mosquito bites</a> every other summer will reduce the spread of Murray Valley encephalitis virus too.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/mozzies-biting-heres-how-to-choose-a-repellent-and-how-to-use-it-for-the-best-protection-150183">Mozzies biting? Here's how to choose a repellent (and how to use it for the best protection)</a>
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<p>Those spending lots of time outdoors face the greatest risk. To <a href="https://www.health.nsw.gov.au/Infectious/mosquito-borne/Pages/bite-prevention.aspx">reduce mosquito bites</a>:</p>
<ul>
<li><p>avoid outdoor activity at dusk and during evening near wetlands or bushland areas where mosquitoes are active</p></li>
<li><p>cover up with light coloured, loose-fitting, long-sleeved shirts with long pants and covered shoes</p></li>
<li><p>use topical insect repellents containing diethytoluamide, picaridin, or oil of lemon eucalyptus. These formulations will provide the longest-lasting protection against mosquito bites if applied to all exposed areas of skin</p></li>
<li><p>use insect screens and nets around the home on windows and doors, and while camping</p></li>
<li><p>use “knockdown” insect sprays and plug-in repellent devices indoors or in sheltered outdoor areas.</p></li>
</ul>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/hSag2Nx4DHs?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">You can reduce your risk of Murray Valley encephalitis in the same way you’d protect yourself from other diseases spread by mosquitoes.</span></figcaption>
</figure>
<p>The risk of Murray Valley encephalitis virus will remain for months ahead. It’s not until the colder weather of autumn arrives that mosquito populations will decline and with them the risks of disease.</p>
<p>Perhaps the <a href="https://www.theguardian.com/australia-news/2023/jan/04/australia-could-swing-from-three-years-of-la-nina-to-hot-and-dry-el-nino-in-2023">return of El Niño dominated weather patterns</a> in coming years, with less rainfall and fewer favourable breeding spots for mosquitoes and waterbirds, the virus will disappear from southeastern Australia. But for how long?</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/feel-like-youre-a-mozzie-magnet-its-true-mosquitoes-prefer-to-bite-some-people-over-others-128788">Feel like you're a mozzie magnet? It's true – mosquitoes prefer to bite some people over others</a>
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</p>
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<img src="https://counter.theconversation.com/content/197894/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Cameron Webb and the Department of Medical Entomology, NSW Health Pathology, have been engaged by a wide range of insect repellent and insecticide manufacturers to provide testing of products and provide expert advice on mosquito biology. Cameron has also received funding from local, state and federal agencies to undertake research into mosquito-borne disease surveillance and management.</span></em></p>Murray Valley encephalitis has been detected in south-eastern Australia. No human cases have yet been reported, but past outbreaks after floods show we need to be cautious.Cameron Webb, Clinical Associate Professor and Principal Hospital Scientist, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1946892022-12-07T13:53:51Z2022-12-07T13:53:51ZMosquitoes are not repelled by vitamins and other oral supplements you might take<figure><img src="https://images.theconversation.com/files/499541/original/file-20221207-11795-5gitd3.jpg?ixlib=rb-1.1.0&rect=1077%2C565%2C4913%2C3422&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">It's only wishful thinking that you can ward off mosquitoes from within.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/aedes-aegypti-mosquito-close-up-a-mosquito-sucking-royalty-free-image/831023822">frank600/iStock via Getty Images Plus</a></span></figcaption></figure><p>A longstanding medical myth suggests that taking vitamin B1, also known as thiamine, can make your body repel mosquitoes.</p>
<p>A “<a href="http://doi.org/10.1001/jama.1966.03100160106030">systemic repellent</a>” that makes your whole body unappealing to biting insects certainly sounds good. Even if you correctly reject the <a href="https://doi.org/10.1186/s12936-020-03217-5">misinformation</a> questioning <a href="https://doi.org/10.4269/ajtmh.1998.59.323">safe</a> and <a href="https://doi.org/10.1056/nejm200207043470102">effective</a> <a href="https://www.epa.gov/insect-repellents/deet">repellents</a> like <a href="https://doi.org/10.1186/1756-3305-7-173">DEET</a>, oral repellents would still have the benefit that you wouldn’t need to worry about covering every inch of exposed skin or carrying containers of bug spray whenever you venture into the great outdoors.</p>
<hr>
<iframe id="noa-web-audio-player" style="border: none" src="https://embed-player.newsoveraudio.com/v4?key=x84olp&id=https://theconversation.com/why-are-some-people-mosquito-magnets-and-others-unbothered-a-medical-entomologist-points-to-metabolism-body-odor-and-mindset-187957&bgColor=F5F5F5&color=D8352A&playColor=D8352A" width="100%" height="110px"></iframe>
<p><em>You can listen to more articles from The Conversation, narrated by Noa, <a href="https://theconversation.com/us/topics/audio-narrated-99682">here</a>.</em></p>
<hr>
<p>Along with thiamine, other alleged oral mosquito repellents include <a href="https://doi.org/10.1055/s-0039-3399744">brewer’s yeast</a>, which contains thiamine, and <a href="https://doi.org/10.1001/jama.285.1.39">garlic</a>, the legendary <a href="https://europepmc.org/article/med/7825135">vampire repellent</a>.
If oral repellents sound too good to be true, it’s because they are. </p>
<p><a href="https://scholar.google.com/citations?user=TSIGUnYAAAAJ&hl=en&oi=ao">As a professor of entomology</a> in Taiwan, where the mosquito-transmitted Dengue virus is endemic, I was curious what science really says about food-based repellents. After a very deep dive into the literature and reading practically every paper ever written on the subject, I compiled this knowledge into the first <a href="https://doi.org/10.1017/S0007485321001176">systematic review</a> of the subject.</p>
<p>The scientific consensus is, unequivocally, that oral repellents don’t exist. Despite <a href="https://doi.org/10.5281/zenodo.7403167">extensive searches</a>, no <a href="http://doi.org/10.1371/journal.pntd.0006247">food, supplement</a>, <a href="https://doi.org/10.4269/ajtmh.1968.17.461">medication, or condition</a> has ever been proven to make people repellent. People with vitamin B1 deficiency don’t attract more mosquitoes, either. </p>
<p>So where did the myth that mosquitoes hate vitamins come from, and why is it so hard to exterminate?</p>
<h2>Making of a myth</h2>
<p>In 1943, Minnesota pediatrician <a href="https://doi.org/10.5281/zenodo.7313319">W. Ray Shannon</a> gave 10 patients varying doses of thiamine, which had only <a href="https://doi.org/10.1159/000343109">first been synthesized</a> seven years prior. They reported back that it relieved itching and prevented further mosquito bites. In 1945, California pediatrician <a href="https://doi.org/10.5281/zenodo.7403108">Howard Eder</a> claimed 10 milligram doses could protect people from fleas. In Europe in the 1950s, physician <a href="https://doi.org/10.5281/zenodo.7403124">Dieter Müting</a> claimed that daily 200 milligram doses kept him bite-free while vacationing in Finland, and hypothesized a breakdown product of thiamine was expelled through the skin.</p>
<p>These findings drew rapid attention, and almost immediate repudiation. The U.S. Naval Medical Research Institute <a href="https://doi.org/10.1126/science.100.2590.147.a">tried to replicate Shannon’s findings, but failed</a>. By 1949, Californians using thiamine to repel fleas from dogs were reporting it as “<a href="https://doi.org/10.1001/archderm.1949.01530070124012">completely worthless</a>.” Controlled studies from <a href="https://pubmed.ncbi.nlm.nih.gov/13568728/">Switzerland</a> to <a href="https://pubmed.ncbi.nlm.nih.gov/4733214/">Liberia</a> repeatedly failed to find any effects at any dose. The first <a href="https://doi.org/10.5281/zenodo.7403142">clinical trial</a> in 1969 concluded definitively that “vitamin B1 is not a systemic mosquito repellent in man,” and <a href="https://doi.org/10.2987/8756-971X(2005)21%5B213:TVBAAH%5D2.0.CO;2">all controlled studies since</a> suggest the same for thiamine, <a href="https://pubmed.ncbi.nlm.nih.gov/6885593/">brewer’s yeast</a>, <a href="https://doi.org/10.1111/j.0269-283X.2005.00544.x">garlic</a>, and <a href="https://doi.org/10.1024/0040-5930.62.11.713">other</a> <a href="https://doi.org/10.1093/pch/19.6.326">alternatives</a>. </p>
<p>The evidence was so overwhelming that, in 1985, the <a href="https://doi.org/10.1016/B978-0-323-54696-6.00006-9">U.S. Food and Drug Administration declared</a> all oral insect repellents are “<a href="https://tile.loc.gov/storage-services/service/ll/fedreg/fr050/fr050116/fr050116.pdf#page=140">not generally recognized as safe and effective and are misbranded</a>,” making labeling supplements as repellents technically fraud.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/499542/original/file-20221207-27-o3hgzd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="foods including egg, lentils, nuts and a " src="https://images.theconversation.com/files/499542/original/file-20221207-27-o3hgzd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/499542/original/file-20221207-27-o3hgzd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/499542/original/file-20221207-27-o3hgzd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/499542/original/file-20221207-27-o3hgzd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/499542/original/file-20221207-27-o3hgzd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/499542/original/file-20221207-27-o3hgzd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/499542/original/file-20221207-27-o3hgzd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Along with being in poultry and pork, B1 is found in many whole grains and legumes.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/products-and-ingredients-containing-vitamin-b1-and-royalty-free-image/668509672">ratmaner/iStock via Getty Images Plus</a></span>
</figcaption>
</figure>
<h2>Medical mechanisms aren’t there</h2>
<p>Scientists know much more about both mosquitoes and vitamins today than ever before.</p>
<p>Vitamin B1 <a href="https://www.ncbi.nlm.nih.gov/books/NBK482360/">does not break down in the body</a> and has <a href="https://doi.org/10.1021/bi401618y">no known effect on skin</a>. The body strongly regulates it, absorbing little ingested thiamine after the first 5 milligrams and <a href="https://doi.org/10.1177/0884533611426149">quickly excreting any excess</a> via urine, so it <a href="https://doi.org/10.1177/0885066616659429">does not build up</a>. Overdose is almost impossible.</p>
<p>As in humans, thiamine is an <a href="https://doi.org/10.1093/aesa/70.4.541">essential nutrient</a> <a href="https://doi.org/10.1093/aesa/52.1.26">for mosquitoes</a>. There is no reason they would fear it or try to avoid it. Nor is there evidence that they can smell it.</p>
<p>The best sources of thiamine are <a href="https://doi.org/10.3390/nu12092810">whole grains, beans, pork, poultry and eggs</a>. If eating a carnitas burrito won’t make you repel mosquitoes, then neither should a pill.</p>
<p>What explains the early reports, then? Along with shoddy experimental design, many used anecdotal patient reports of fewer bite symptoms as a proxy for reduced biting, which is not a good way to get an accurate picture of what’s going on.</p>
<p>Mosquito bites are followed by <a href="https://doi.org/10.1111/j.1346-8138.1989.tb01251.x">two reactions</a>: an immediate reaction that starts fast and lasts hours and a delayed reaction lasting days. The presence and intensity of these reactions depends not on the mosquito, but on your own immune system’s familiarity with that particular species’ saliva. With age and continued exposure, the body goes from no reaction, to delayed reaction only, to both, to immediate reaction only, and eventually no reaction.</p>
<p>What Shannon and others thought was repellency could have been <a href="https://doi.org/10.3109/07853899409147906">desensitization</a>: The patients were still getting bitten, they just stopped showing symptoms.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/499543/original/file-20221207-27-w8izk8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="woman with backpack in woods sprays her arm" src="https://images.theconversation.com/files/499543/original/file-20221207-27-w8izk8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/499543/original/file-20221207-27-w8izk8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/499543/original/file-20221207-27-w8izk8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/499543/original/file-20221207-27-w8izk8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/499543/original/file-20221207-27-w8izk8.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/499543/original/file-20221207-27-w8izk8.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/499543/original/file-20221207-27-w8izk8.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Applying a safe and effective insect repellent to your skin is a proven way to ward off mosquitoes and their bites.</span>
<span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/photo/woman-applies-mosquito-spray-to-her-hands-during-royalty-free-image/1404334863">SimpleImages/Moment via Getty Images</a></span>
</figcaption>
</figure>
<h2>So, what’s the problem?</h2>
<p>Despite the scientific consensus, a 2020 survey of pharmacists in <a href="https://doi.org/10.3390/pharmacy8020094">Australia</a> found that 27% were still recommending thiamine as a repellent to patients traveling abroad: an unacceptable recommendation. Besides wasting money, people relying on vitamins as protection against mosquitoes can still get bitten, potentially putting them at risk of <a href="https://doi.org/10.1001/jama.296.18.2234">diseases</a> like <a href="https://doi.org/10.1155/2003/158926">West Nile</a> and <a href="https://doi.org/10.2310/7060.2000.00074">malaria</a>.</p>
<p>To get around the American ban and widely agreed-upon scientific consensus on oral repellents, some unscrupulous dealers are making thiamine patches or even injections. Unfortunately, while thiamine is safe if swallowed, it <a href="https://doi.org/10.1016/j.alit.2022.01.004">can</a> <a href="https://doi.org/10.1016/S0196-0644(89)80215-X">cause</a> <a href="https://doi.org/10.1016/S0091-6749(95)70111-7">severe</a> <a href="https://doi.org/10.1001/jama.1941.72820340003008a">allergic</a> <a href="https://doi.org/10.1001/archderm.1950.01530120149018">reactions</a> when taken by other routes. <a href="https://doi.org/10.1016/j.actatropica.2012.10.009">These products</a> are thus not only <a href="https://doi.org/10.1093/jisesa/iev125">worthless</a>, but also potentially dangerous.</p>
<p>Not every problem can be solved with food. Long sleeves and <a href="https://doi.org/10.7326/0003-4819-128-11-199806010-00013">bug spray</a> <a href="http://doi.org/10.1056/NEJMoa011699">containing DEET</a>, <a href="http://npic.orst.edu/ingred/picaridin.html">picaridin</a> or <a href="https://www.epa.gov/insect-repellents/skin-applied-repellent-ingredients">other proven repellents</a> are still your best defense against biting pests.</p><img src="https://counter.theconversation.com/content/194689/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Matan Shelomi does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>A medical myth persists that the B vitamin thiamine is a systemic insect repellent that wards off mosquitoes when taken orally. But scientists have disproven this mistaken belief again and again.Matan Shelomi, Associate Professor of Entomology, National Taiwan UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1941752022-12-04T08:54:46Z2022-12-04T08:54:46ZA dangerous pesticide isn’t being monitored in key bird of prey populations - we’re shedding light on that gap<figure><img src="https://images.theconversation.com/files/497025/original/file-20221123-24-5lmmwa.jpg?ixlib=rb-1.1.0&rect=612%2C15%2C2328%2C1215&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">GettyImages</span></span></figcaption></figure><p>It was once regarded as a <a href="https://www.swissinfo.ch/eng/ddt--from-miracle-chemical-to-banned-pollutant/3253684">miracle chemical</a> to protect against disease and improve global food production. The man who discovered its properties even won a <a href="https://www.britannica.com/biography/Paul-Hermann-Muller">Nobel Prize for medicine</a>. But today, <a href="https://www.britannica.com/science/DDT">dichlorodiphenyltrichloroethane</a> (DDT) is best known for its devastating effects on the environment, as well as on animal and human health. </p>
<p>It was first used in the second world war to protect Allied soldiers against malaria and typhus, which are spread by mosquitoes and body lice. After the war, DDT became a widely available pesticide to kill insect crops pests and insects causing disease in humans. </p>
<p>However, it became clear that DDT was toxic to more than its intended targets. Continued exposure to the chemical <a href="https://www.cdc.gov/biomonitoring/pdf/ddt_factsheet.pdf">can cause</a> neurological damage, endocrine disorders and reproductive failure in both humans and animals. </p>
<p>Awareness of this damage was in no small part due to Rachel Carson’s book <a href="http://www.rachelcarson.org/SilentSpring.aspx">Silent Spring</a>, published in 1962. Silent Spring brought global attention to DDT’s environmental impacts and sparked a public outcry that forced much of the developed world – the “global north” – to ban the use of DDT in the 1970s and 1980s.</p>
<p>In 2004 the <a href="http://www.pops.int/">Stockholm Convention</a> on Persistent Organic Pollutants – those that stay in the environment for a long time after use – was adopted by over 90 nations. DDT was among the most dangerous pesticides, industrial chemicals and by-products placed on the convention’s “dirty dozen” list, and was banned in most parts of the world.</p>
<p>Two years later the World Health Organization <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1570869/">recommended</a> the restricted use of DDT to control malaria. It <a href="http://npic.orst.edu/factsheets/ddtgen.pdf">remains in use</a> for this purpose in various tropical countries in Asia, Africa, and South and Central America. Its use here doesn’t just put human health at risk: top predators, among them <a href="https://www.britannica.com/animal/bird-of-prey">birds of prey</a> (also referred to as raptors), are threatened too.</p>
<h2>Birds of prey as sentinels</h2>
<p>Birds of prey or raptors are often apex predators, sitting at the top of the food chain. As such, they can act as an “ecological barometer”, helping us gauge the health of the environment. In addition to their value as indicator species, they provide valuable ecosystem services, controlling pest animals such as rodents and removing carrion from the environment, potentially reducing the spread of disease. </p>
<p>Because DDT accumulates in wildlife and magnifies up the food chain many raptor populations have been nearly <a href="https://www.jstor.org/stable/2401613#metadata_info_tab_contents">wiped out</a> by its use. However, this <a href="https://www.nationalgeographic.org/activity/biomagnification-and-bioaccumulation/">bio-accumulation</a> also means they have the potential to serve as a useful indicator to monitor levels of DDT in the environment. Thus, raptors can be regarded as sentinels for DDT.</p>
<p>There has been extensive monitoring of DDT in raptors by conservation agencies and academics across the globe for the last 60 years. But no study has looked at the patterns emerging from these monitoring programmes, nor compared these patterns through space and time. Our <a href="https://www.sciencedirect.com/science/article/pii/S0048969722068346">new study</a> fills that gap. </p>
<h2>A global north bias</h2>
<p>We found that DDT monitoring in raptors is heavily biased toward the global north. Europe and North America account for 95% of samples. This is a concern because most DDT use is currently in the global south, as are most raptor species. </p>
<p>We found that DDT has been measured in over 27,000 raptors across more than 100 species. The numbers of birds sampled peaked in the 1960s and 1970s, an increase that coincided with international concern surrounding DDT.</p>
<p>However, just three species account for half of all raptor samples collected: bald eagle, Eurasian sparrowhawk and peregrine falcon. Only the peregrine falcon occurs on all continents, but have been sampled far less in Africa, Asia, Central and South America than Europe and North America. The Eurasian sparrowhawk is also found in Asia but similar to the peregrine has been sampled far less frequently there than in Europe.</p>
<p>The geographical one-sidedness <a href="https://tspace.library.utoronto.ca/bitstream/1807/71107/1/Tackling%20Inequities%20in%20Global%20Scientific%20Power%20Structures.pdf">we’ve identified</a> can likely be linked to a dearth of available funding, appropriate infrastructure and the necessary training in global south nations.</p>
<p>And it’s worrying for three reasons. </p>
<p>First, <a href="https://reader.elsevier.com/reader/sd/pii/S0006320718305871?token=BE5B91A7D1D04D803F09245532FF85F05E7C3CC99FD685A3963349EE2107B039AB93376274699582A842DCBC230F5AAE&originRegion=us-east-1&originCreation=20221115162212">most current DDT use</a> is in the global south because of the chemical’s role in malaria control. </p>
<p>Second, the region is <a href="https://reader.elsevier.com/reader/sd/pii/S0006320718305871?token=BE5B91A7D1D04D803F09245532FF85F05E7C3CC99FD685A3963349EE2107B039AB93376274699582A842DCBC230F5AAE&originRegion=us-east-1&originCreation=20221115162212">home to most</a> of the world’s raptors. Most raptor species <a href="https://www.pnas.org/doi/epdf/10.1073/pnas.2018203118">come from</a> South and Southeast Asia, followed by sub-Saharan Africa and South America. The tropics in particular (mostly in the global south) display the <a href="https://www.pnas.org/doi/epdf/10.1073/pnas.2018203118">highest</a> raptor diversity. There are also many declines of species in these <a href="https://www.sciencedirect.com/science/article/abs/pii/S0006320718300934">regions</a>.</p>
<p>Third, many countries in the global south are notoriously <a href="https://www.adb.org/sites/default/files/publication/514476/adbi-wp980.pdf">poor enforcers</a> of environmental legislation.</p>
<h2>More gaps to fill</h2>
<p>Even with better enforcement, global north countries are not always good at protecting their environments. It was only when peregrine falcons were wiped out from many regions of the <a href="https://www.rspb.org.uk/birds-and-wildlife/wildlife-guides/bird-a-z/peregrine/population-numbers-and-trends/">UK</a> and the <a href="https://kids.frontiersin.org/articles/10.3389/frym.2022.714834">US</a> – in the late 1950s to mid 1960s – that their governments finally acted by banning DDT.</p>
<p>As more data are being gathered and collated to develop a clearer picture of DDT levels among <a href="https://doi.org/10.1016/j.envpol.2017.09.059">raptors</a> in the global south, countries in the region might learn from the US and UK measures and prepare similar programmes to start monitoring DDT levels in their raptor populations in a more systematic manner.</p>
<p>Our research is a critical first step in consolidating the uneven information on the global monitoring of DDT. The next step will be to compare how DDT levels in raptors from tropical regions still using DDT compare to levels in raptors from more temperate regions where DDT has long been banned. We are currently working on that research. </p>
<p>As more data becomes available and a clearer picture is created, we hope governments will feel compelled to act to ensure we do not face a second “silent spring”.</p><img src="https://counter.theconversation.com/content/194175/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Kailen Padayachee received funding from the National Research Foundation and Carnegie Corporation of New York. </span></em></p><p class="fine-print"><em><span>Arjun Amar receives funding from the South African National Research Foundation (NRF) . </span></em></p><p class="fine-print"><em><span>Chevonne Reynolds does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>DDT accumulates in wildlife and magnifies up the food chain. Birds of prey occupy the top of these food chains in various ecosystems.Kailen Padayachee, PhD Candidate, FitzPatrick Institute, University of Cape Town and Research Fellow, School of Animal, Plant and Environmental Sciences, University of the WitwatersrandArjun Amar, Associate Professor , FitzPatrick Institute of African Ornithology, University of Cape TownChevonne Reynolds, Senior Lecturer, University of the WitwatersrandLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1945172022-11-17T19:05:52Z2022-11-17T19:05:52ZMozzies are everywhere right now – including giant ones and those that make us sick. Here’s what you need to know<figure><img src="https://images.theconversation.com/files/495731/original/file-20221116-24-uffsj2.JPG?ixlib=rb-1.1.0&rect=388%2C232%2C4788%2C2956&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Cameron Webb (NSW Health Pathology)</span>, <span class="license">Author provided</span></span></figcaption></figure><p>Like all insects, mosquitoes thrive in warmer weather. But what they really need is water. La Niña <a href="https://www.abc.net.au/news/2022-09-18/rain-forecast-when-la-nina-end-summer-flooding/101446044">rainfall</a> and flooding are providing the perfect breeding ground for mosquitoes, with numbers exploding in recent weeks.</p>
<p><div data-react-class="Tweet" data-react-props="{"tweetId":"1592747103457251328"}"></div></p>
<p>People are also seeing giant mosquitoes, tiny mosquitoes, and species they haven’t noticed before. Some of these mosquitoes are around every season but their numbers are booming, thanks to the favourable conditions. </p>
<p>Australia has around <a href="https://www.publish.csiro.au/book/6391/">300 species of mosquito</a>. So which do you need to look out for? </p>
<p>First, let’s go over some mozzie basics. </p>
<h2>Mozzies live for around 3 weeks</h2>
<p>The mosquito life cycle is complex. Eggs are laid on or around water. When immature mosquitoes hatch, they’re completely reliant on being in water. </p>
<p>During the warmer months, it may take as little as a week for an adult mosquito to emerge from the water to start buzzing and biting. </p>
<p>Adult mosquitoes only live for about three weeks.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/495378/original/file-20221115-17-1ejkc7.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/495378/original/file-20221115-17-1ejkc7.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=337&fit=crop&dpr=1 600w, https://images.theconversation.com/files/495378/original/file-20221115-17-1ejkc7.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=337&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/495378/original/file-20221115-17-1ejkc7.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=337&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/495378/original/file-20221115-17-1ejkc7.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/495378/original/file-20221115-17-1ejkc7.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/495378/original/file-20221115-17-1ejkc7.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The immature stages of mosquitoes (commonly known as wrigglers) are only found in water.</span>
<span class="attribution"><span class="source">Cameron Webb (NSW Health Pathology)</span></span>
</figcaption>
</figure>
<h2>Only females bite</h2>
<p>As well as water and warmth, mosquitoes also need blood. But only female mosquitoes bite, as they need the extra nutritional hit to help develop eggs. </p>
<p>Mosquitoes don’t just bite <a href="https://theconversation.com/feel-like-youre-a-mozzie-magnet-its-true-mosquitoes-prefer-to-bite-some-people-over-others-128788">people</a>. They will <a href="https://parasitesandvectors.biomedcentral.com/articles/10.1186/s13071-019-3405-z">bite a wide range</a> of mammals, birds, reptiles and amphibians. They can even <a href="https://blogs.ifas.ufl.edu/news/2018/07/12/uf-study-mosquito-that-feeds-on-worms-leeches-can-carry-deadly-diseases/">bite earthworms</a>, <a href="https://pubmed.ncbi.nlm.nih.gov/15264621/">mudskippers</a> (amphibious fish) and maybe even <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3381582/">whales</a>.</p>
<h2>What are ‘giant’ mosquitoes?</h2>
<p>One mosquito in Australia that doesn’t bite at all is <em>Toxorhynchites speciosus</em>, <a href="https://cameronwebb.wordpress.com/2019/02/11/giant-mosquitoes-are-invading-my-backyard/">a “giant” mosquito</a>, common in eastern Australia. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/495736/original/file-20221116-12-69nnis.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/495736/original/file-20221116-12-69nnis.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/495736/original/file-20221116-12-69nnis.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/495736/original/file-20221116-12-69nnis.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/495736/original/file-20221116-12-69nnis.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/495736/original/file-20221116-12-69nnis.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/495736/original/file-20221116-12-69nnis.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The largest mosquito in Australia is <em>Toxorhynchites speciosus</em>. Lucky for us, it doesn’t bite.</span>
<span class="attribution"><span class="source">Tess Pillekom</span></span>
</figcaption>
</figure>
<p>The mosquito is predatory: their “wrigglers” often eat those of other pest mosquitoes. Closely related mosquitoes have even been used for <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7693308/">mosquito control</a> in other counties.</p>
<p>But it isn’t these “friendly” mosquitoes causing all the problems after flooding. </p>
<p>Other mosquitoes, commonly known as “floodwater mosquitoes”, can bite and are found in large swarms following flooding. They’re a <a href="https://www.abc.net.au/news/2022-11-01/brisbane-mosquito-and-midge-invasion-due-to-warm-wet-weather/101600898">serious nuisance</a>. Examples of these mosquitoes include <a href="https://www.inaturalist.org/taxa/833603-Aedes-sagax"><em>Aedes sagax</em></a>, <a href="https://www.inaturalist.org/taxa/1112146-Aedes-vittiger"><em>Aedes vittiger</em></a>, and <a href="https://www.inaturalist.org/taxa/1127332-Aedes-aculeatus"><em>Aedes aculeatus</em></a>. They often disappear as quickly as they appear.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/495730/original/file-20221116-12-t72dkx.JPG?ixlib=rb-1.1.0&rect=760%2C457%2C3569%2C2661&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/495730/original/file-20221116-12-t72dkx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/495730/original/file-20221116-12-t72dkx.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/495730/original/file-20221116-12-t72dkx.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/495730/original/file-20221116-12-t72dkx.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/495730/original/file-20221116-12-t72dkx.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/495730/original/file-20221116-12-t72dkx.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A large and distinctive mosquito, <em>Aedes vittiger</em>, can cause serious pest problems after flooding.</span>
<span class="attribution"><span class="source">Cameron Webb (NSW Health Pathology)</span></span>
</figcaption>
</figure>
<p>Mosquito surveillance programs, such as the <a href="https://www.health.nsw.gov.au/Infectious/mosquito-borne/Pages/surveillance.aspx">NSW Arbovirus Surveillance and Mosquito Monitoring Program</a>, are picking up these mosquitoes (and lots of smaller species) already this season. Perhaps the most famous of them all is the large, sandy-coloured mosquito <em>Aedes alternans</em>. Commonly known as the Hexham Grey, this mosquito has had <a href="https://hunterheadline.com.au/blog-post/ossie-the-mossie-comes-of-age/">poems written about it</a> and there is even a “<a href="https://365project.org/onewing/365/2014-10-06">big mozzie</a>” in Hexham, NSW.</p>
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Read more:
<a href="https://theconversation.com/a-wet-spring-and-summer-means-more-mosquitoes-but-now-weve-got-japanese-encephalitis-virus-to-worry-about-too-191510">A wet spring and summer means more mosquitoes but now we've got Japanese encephalitis virus to worry about too</a>
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<h2>Which mosquitoes make us sick?</h2>
<p>Despite the diversity of mosquitoes in Australia, only a few pose a serious public health threat.</p>
<p><em>Aedes notoscriptus</em> mosquitoes have given up their natural habitat and <a href="https://theconversation.com/hidden-housemates-the-mosquitoes-that-battle-for-our-backyards-59072">adapted</a> to life in water-filled containers around our homes. They’ve proven to nuisance-biting pests as well as <a href="https://academic.oup.com/jme/article/35/2/104/2221688?">transmitting viruses</a> that make us sick.</p>
<p>In coastal regions of Australia, <em>Aedes vigilax</em> (commonly known as the saltmarsh mosquito) and <em>Aedes camptorhynchus</em> (commonly known as the southern saltmarsh mosquito) are found in estuarine wetlands. These include mangrove and saltmarsh habitats where water is often brought in with “<a href="https://media.bom.gov.au/social/blog/1603/explainer-king-tides/">king tides</a>”. The mosquitoes tolerate the salty conditions. These mosquitoes can emerge in huge numbers in summer, are aggressive biters, and can <a href="https://pubmed.ncbi.nlm.nih.gov/31095691/">fly many kilometres from wetlands</a>. They are also the mosquito most likely to be causing outbreaks of mosquito-borne disease in coastal regions due to <a href="https://pubmed.ncbi.nlm.nih.gov/6291499/">their ability to spread Ross River virus</a>. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/495376/original/file-20221115-11-k0m3vp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/495376/original/file-20221115-11-k0m3vp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=328&fit=crop&dpr=1 600w, https://images.theconversation.com/files/495376/original/file-20221115-11-k0m3vp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=328&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/495376/original/file-20221115-11-k0m3vp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=328&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/495376/original/file-20221115-11-k0m3vp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=412&fit=crop&dpr=1 754w, https://images.theconversation.com/files/495376/original/file-20221115-11-k0m3vp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=412&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/495376/original/file-20221115-11-k0m3vp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=412&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">The saltmarsh mosquito (<em>Aedes vigilax</em>) taking a chance to grab a blood meal.</span>
<span class="attribution"><span class="source">Cameron Webb (NSW Health Pathology)</span></span>
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<p>There are a number of pest mosquitoes found in freshwater wetlands. The biggest pest is <em>Culex annulirostris</em> (commonly known as the banded freshwater mosquito). This mosquito is found in a range of habitats, from wetlands to stagnant puddles. The banded freshwater mosquito is probably the most important species when it comes to spreading pathogens such as <a href="https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1005070">Ross River virus</a>, <a href="https://theconversation.com/explainer-what-is-murray-valley-encephalitis-virus-112212">Murray Valley encephalitis</a> virus, and <a href="https://theconversation.com/japanese-encephalitis-virus-has-been-detected-in-australian-pigs-can-mozzies-now-spread-it-to-humans-178017">Japanese encephalitis virus</a>.</p>
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Read more:
<a href="https://theconversation.com/how-to-mozzie-proof-your-property-after-a-flood-and-cut-your-risk-of-mosquito-borne-disease-178299">How to mozzie-proof your property after a flood and cut your risk of mosquito-borne disease</a>
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<h2>How can we beat their bites?</h2>
<p>After three years of above average rainfall, and recently flooding, most of eastern Australia is just one giant mosquito habitat. While some efforts to use insecticides to control mosquitoes may be effective, the reality is the task of adequately controlling mosquito numbers is insurmountable.</p>
<p>There are some steps you can take to protect yourself and family from mosquito bites. When outdoors, wear a loose-fitting long sleeved shirt, long pants, and covered shoes. You can even <a href="https://theconversation.com/mozzie-repellent-clothing-might-stop-some-bites-but-youll-still-need-a-cream-or-spray-107266">treat your clothing with chemicals</a> such as permethrin or transfluthrin. </p>
<p>Insect repellents also provide protection. Products that contain deet, picaridin, or lemon eucalyptus oil <a href="https://theconversation.com/mozzies-biting-heres-how-to-choose-a-repellent-and-how-to-use-it-for-the-best-protection-150183">will provide the longest-lasting protection</a> but ensure you cover all exposed areas of skin. </p>
<p><a href="https://theconversation.com/insect-repellents-work-but-there-are-other-ways-to-beat-mosquitoes-without-getting-sticky-171805">Mosquito coils and other products may help</a> when paired with repellents.</p>
<p>Now the bad news. The floods may pass quickly but the water is going to remain in pools and puddles across much of eastern Australia for most of the summer. That is great news for mosquitoes but not so good for those of us already nursing arms and legs full of itchy red mosquito bites.</p><img src="https://counter.theconversation.com/content/194517/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Cameron Webb and the Department of Medical Entomology, NSW Health Pathology, have been engaged by a wide range of insect repellent and insecticide manufacturers to provide testing of products and provide expert advice on mosquito biology. Cameron has also received funding from local, state and federal agencies to undertake research into mosquito-borne disease surveillance and management.</span></em></p>Rain and floods mean mozzie numbers are booming. Australia has around 300 different mosquito species, but they can’t all make us sick, or even bite.Cameron Webb, Clinical Associate Professor and Principal Hospital Scientist, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1940662022-11-10T13:47:06Z2022-11-10T13:47:06ZClimate change affects mosquito behaviour. This may make it harder to end malaria in South Africa<figure><img src="https://images.theconversation.com/files/494228/original/file-20221108-20-5pc5g2.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Global climate is changing rapidly. This has a range of public health implications. </span> <span class="attribution"><span class="source">CDC/ James Gathany</span></span></figcaption></figure><p>Changes in climatic factors – such as higher temperatures and increased rainfall – affect the developmental, behavioural and distribution patterns of <a href="https://theconversation.com/what-a-warmer-wetter-world-means-for-insects-and-for-what-they-eat-166509">insects</a> like mosquitoes. These changes have serious implications for the effective control of insect-borne diseases such as malaria.</p>
<p>Worryingly, temperatures across southern Africa are predicted to increase by at least <a href="https://www.climatelinks.org/sites/default/files/asset/document/Southern%20Africa%20Climate%20Info%20Fact%20Sheet_FINAL.pdf">0.8⁰C by 2035</a>.</p>
<p>Malaria is currently present in three provinces in South Africa: Limpopo, Mpumalanga and KwaZulu-Natal. Limpopo reports 62% of the local cases, while KwaZulu-Natal reports only <a href="https://malariaelimination8.org/south-africa">6%</a>.</p>
<p>Over the past 50 years annual temperatures in South Africa have been increasing significantly faster than the <a href="https://www.climatelinks.org/sites/default/files/asset/document/Southern%20Africa%20Climate%20Info%20Fact%20Sheet_FINAL.pdf">global average</a>. The increases have been most extreme in Limpopo, where temperatures have risen by an average of 0.12⁰C every decade. Small annual shifts have big effects.</p>
<p>These higher temperatures increase the malaria risk. This is because the malaria mosquito and parasite are happiest at <a href="https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.2003489">temperatures</a> between 17⁰C and 35⁰C. </p>
<p>Warmer weather means vector mosquitoes are able to <a href="https://parasitesandvectors.biomedcentral.com/articles/10.1186/s13071-019-3391-1#:%7E:text=albopictus%20intrinsic%20rate%20of%20growth,females%20in%2027%20%C2%B0C.">develop faster</a>, invade new locations, and spread <a href="https://wellcome.org/news/how-climate-change-affects-vector-borne-diseases">vector-borne diseases</a>.</p>
<p>In addition, increased rainfall will potentially increase the number of mosquito vector <a href="https://wellcome.org/news/how-climate-change-affects-vector-borne-diseases">breeding sites</a>. Vector mosquitoes like those that transmit malaria breed in stagnant and temporary bodies of water. Research in Limpopo has <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6950450/">shown</a> that heavy rains in spring are usually associated with higher malaria case numbers during summer. </p>
<p>The impact of climate change on mosquitoes is very clear. But its impact on malaria transmission is still unclear. Some theoretical mathematical modelling studies <a href="https://www.sciencedirect.com/science/article/abs/pii/S003592030600263X">predict</a> an uptick in malaria case numbers due to climate change. But other models suggest climate change will have <a href="https://www.nature.com/articles/415905a">no impact on malaria</a>. More data are needed to see which model is correct. This is because the effect is difficult to test in the laboratory. </p>
<p>Whether climate change will present another challenge to achieving malaria elimination is yet to be confirmed. Our <a href="https://www.nicd.ac.za/centres/centre-for-emerging-zoonotic-and-parasitic-diseases/">research group</a> is currently trying to address this knowledge gap.</p>
<h2>What we do know</h2>
<p>The relationship between climate change and malaria is complicated. But four things are clear: as the Earth warms up the malaria vector will develop faster, allowing them to breed faster, bite <a href="https://wellcomeopenresearch.org/articles/2-102#ref-35">more frequently</a> and expand into formerly unsuitable habitats. </p>
<p>This means that mosquito larvae will develop into adults faster. The sooner the female bites, the sooner she can transmit the disease. If she bites more frequently, she will spread more disease. </p>
<p>The malaria parasite’s development inside the mosquito is highly dependent on temperature. At temperatures <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5658182/">below 17⁰C, and above 35⁰C</a>, the parasite’s life cycle inside the mosquito cannot be completed. This halts the onward transmission of malaria. </p>
<p>The mosquito’s transformation from larva to free-flying adult generally occurs at temperatures between <a href="https://www.cambridge.org/core/journals/bulletin-of-entomological-research/article/abs/effect-of-temperature-on-the-development-of-the-aquatic-stages-of-anopheles-gambiae-sensu-stricto-diptera-culicidae/6375ECAEF9B542ABB63F074E0972C855">22⁰C and 34⁰C</a>. Interestingly, research has <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3146900/">shown</a> that mosquitoes can change their behaviour to spend most of their time resting in cooler spaces. This way they can survive when ambient temperatures increase. This behaviour of the mosquito can help the parasite survive temperatures that would otherwise stop its development. </p>
<p>Distinct changes in the <a href="https://geographical.co.uk/climate-change/as-the-world-warms-the-seasons-are-shifting">seasons</a>, largely due to climate change, have been noted. The <a href="https://www.climatelinks.org/sites/default/files/asset/document/Southern%20Africa%20Climate%20Info%20Fact%20Sheet_FINAL.pdf">southern African region</a> is experiencing more frequent extreme heat days and fewer extreme cool days.</p>
<p>Therefore, winters are becoming much warmer, allowing mosquitoes to breed and transmit malaria in larger numbers during the winter months. Summer months are also getting hotter. In some cases, the summers may get too hot for mosquito and parasite growth, preventing malaria transmission. Climate change could cause a shift in the malaria transmission season from the summer months to the traditionally cooler autumn and winter months.</p>
<p>Rainfall also plays a major role in malaria transmission. In general, malaria incidence decreases during the El Niño (hotter but drier) years and increases in the La Niña (cooler but wetter) <a href="https://www.sciencedirect.com/science/article/abs/pii/S003592030600263X">years</a>. This is particularly true in countries like South Africa, where the adaptable malaria vector, <em>Anopheles arabiensis</em>, is a dominant transmitting vector. South Africa is currently in a La Niña cycle, so the upcoming malaria season (October to February) could potentially be significant, given the more favourable conditions for malaria transmission and the relaxation of all COVID-related restrictions on movement. </p>
<h2>The South African situation</h2>
<p>Our research group based at the <a href="https://www.nicd.ac.za/centres/centre-for-emerging-zoonotic-and-parasitic-diseases/">National Institute for Communicable Diseases</a> and the University of Witwatersrand’s <a href="https://www.wits.ac.za/wrim/">Research Institute for Malaria</a> was involved in identifying the mosquitoes behind the malaria epidemic of <a href="https://resjournals.onlinelibrary.wiley.com/doi/abs/10.1046/j.1365-2915.2000.00234.x?sid=nlm%3Apubmed">2000</a>. This outbreak coincided with severe <a href="https://earth.esa.int/web/earth-watching/natural-disasters/floods/content/-/asset_publisher/zaoP2lUloYKv/content/flood-mozambique-february-2000/">flooding</a> in southern Mozambique. The dramatic increase in available breeding sites allowed an insecticide-resistant mosquito from Mozambique, <em>Anopheles funestus</em>, to reinvade KwaZulu-Natal, driving malaria case numbers up.</p>
<p>Since this outbreak, our group has been conducting <a href="https://sajs.co.za/article/view/11755">intensive surveillance</a> in South Africa’s endemic provinces. We’ve also been involved in research to understand the impact of climate change on malaria transmission in South Africa. </p>
<p>Research from our vector laboratories has <a href="https://malariajournal.biomedcentral.com/articles/10.1186/s12936-018-2250-4">demonstrated</a> that a warmer world would reduce the effectiveness of insecticides used for indoor residual spraying. In addition, insecticide resistant mosquitoes <a href="https://malariajournal.biomedcentral.com/articles/10.1186/s12936-017-1720-4%20">seem better adapted</a> to surviving the warmer conditions than mosquitoes that are sensitive to insecticides.</p>
<p>Modelling experiments <a href="https://previous.iiasa.ac.at/web/scientificUpdate/2014/Abiodun_Gbenga.html">suggest</a> that humidity levels will also influence malaria transmission in South Africa. But this needs to be confirmed under laboratory conditions using live mosquitoes.</p>
<h2>What needs to be done?</h2>
<p>It is clear that the relationship between climate change and malaria is complex. More work needs to be done to understand this relationship so effective control measures can be put in place. Crucially, malaria hotspots should be targeted for surveillance in order to understand the role of microclimate on <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3146900/">malaria transmission</a>. Microclimate is a set of local climate conditions that may differ from the climate in general. </p>
<p>At present, there is no evidence that the <a href="https://www.nicd.ac.za/wp-content/uploads/2018/12/south_africa_malaria_risk_dec2018_final.pdf">malaria-risk areas</a> in South Africa have expanded. However, regardless of the climate or whether you have travelled this summer, it is critical to think about malaria when it comes to unexplained fevers. <a href="https://www.nicd.ac.za/uploads/2017/03/Malaria-FAQ-NICD-Nov-2018.pdf">Know</a> what the symptoms of malaria are, how to reduce the risk of being infected, and what to do if you suspect that you have malaria.</p><img src="https://counter.theconversation.com/content/194066/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Shüné Oliver receives funding from the National Research Foundation of South Africa, the National Health Laboratory Services Research Trust and the Female Academic Fellowship (FALF). </span></em></p><p class="fine-print"><em><span>Jaishree Raman is affiliated with National Institute for Communicable Diseases, the Wits Research Institute for Malaria and the UP Institute for Sustainable Malaria Control. She receives funding from the Global Fund, the Bill and Melinda Gates Foundation, the South African Medical Research Council, the South Africa Research Trust, the National Research Foundation and the National Institute for Communicable Diseases.</span></em></p>As the Earth warms up the malaria vector will develop faster, allowing them to breed faster, bite more frequently and expand into formerly unsuitable habitats.Shüné Oliver, Medical scientist, National Institute for Communicable DiseasesJaishree Raman, Principal Medical Scientist and Head of Laboratory for Antimalarial Resistance Monitoring and Malaria Operational Research, National Institute for Communicable DiseasesLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1933992022-11-04T06:57:52Z2022-11-04T06:57:52ZMalaria in Africa: why most countries haven’t beaten it yet<figure><img src="https://images.theconversation.com/files/492516/original/file-20221031-21-j9vutx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">80% of malaria deaths are in children younger than five. </span> <span class="attribution"><span class="source">Olympia de Maismont/AFP via Getty Images</span></span></figcaption></figure><p>Malaria remains one of the most devastating parasitic diseases affecting humans. In 2020 there were around 241 million cases and 672,000 malaria-related deaths. This is a sharp <a href="https://www.who.int/publications/i/item/9789240040496">increase</a> from 2019. </p>
<p>One reason it’s so persistent is that the malaria parasite has a very <a href="https://www.cdc.gov/malaria/about/biology/index.html#:%7E:text=The%20malaria%20parasite%20life%20cycle,which%20rupture%20and%20release%20merozoites%20">complex life cycle</a>. It involves many different developmental stages and multiple hosts (mosquitoes and humans). </p>
<p>And in Africa, what adds to the challenge of controlling malaria is that the continent is home to some of the most <a href="https://apps.who.int/iris/bitstream/handle/10665/310862/9789241550499-eng.pdf">efficient malaria vectors</a>. These include <em>Anopheles gambiae</em> and <em>An. funestus</em>. Also, the malaria parasite species <em>Plasmodium falciparum</em>, the <a href="https://www.who.int/news-room/fact-sheets/detail/malaria">dominant species</a> in Africa, is the most lethal. It’s responsible for most malaria cases and deaths – 80% of which occur in children younger than five. </p>
<p>The World Health Organization (WHO) acknowledged these factors when it excluded Africa from its first Global Malaria Eradication Campaign, which ran <a href="https://www.cdc.gov/malaria/about/history/">from 1955 until 1969</a>.</p>
<p>Since then, there have been many advances in malaria control. These include long-lasting insecticide treated nets, malaria rapid diagnostic tests and artemisinin-based combination therapies (ACTs) for malaria treatment. </p>
<p>But malaria elimination is still a challenge. Only <a href="https://www.who.int/teams/global-malaria-programme/elimination/countries-and-territories-certified-malaria-free-by-who">two African countries</a>, Algeria and Morocco, have been certified malaria-free by the WHO. </p>
<p>There are many reasons for the elimination targets remaining out of reach. In this article we highlight four: poverty, human movement, resistance and climate change.</p>
<h2>Poverty</h2>
<p>The limited progress towards malaria elimination is not surprising considering that some of the most malaria-burdened countries in Africa are also some of <a href="https://www.malariaconsortium.org/userfiles/file/Past%20events/factsheet2%20-%20malaria%20and%20poverty.pdf">the poorest countries</a> in the world.</p>
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Read more:
<a href="https://theconversation.com/ending-malaria-in-africa-needs-to-focus-on-poverty-quick-fixes-wont-cut-it-169205">Ending malaria in Africa needs to focus on poverty: quick fixes won't cut it</a>
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<p>Malaria is both a cause and a consequence of poverty. The disease will therefore remain a significant problem in Africa, if more is not done to improve the socio-economic status of malaria-affected communities. Eliminating poverty to improve the health and well-being of all are part of both the <a href="https://www.un.org/millenniumgoals/">millennium</a> and <a href="https://sdgs.un.org/goals">sustainable</a> development goals. This should be a priority for governments of malaria-endemic countries.</p>
<h2>Mobility</h2>
<p>Africa has one of the fastest growing populations, with a <a href="https://www.migrationpolicy.org/article/africa-intracontinental-free-movement#:%7E:text=The%20African%20continent%20has%20the,region%20is%20growing%20even%20faster">high level of mobility</a>. Marginalised and vulnerable populations are some of most mobile groups within Africa. They travel vast distances across countries with varying malaria transmission intensities. </p>
<p>Human mobility is strongly associated with the global <a href="https://www.gavi.org/vaccineswork/5-reasons-why-pandemics-like-covid-19-are-becoming-more-likely">spread of infectious diseases</a>, as demonstrated by the recent COVID-19, Ebola and monkeypox outbreaks. This presents a challenge to Africa’s malaria elimination aspirations. </p>
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Read more:
<a href="https://theconversation.com/how-africas-porous-borders-make-it-difficult-to-contain-ebola-118719">How Africa's porous borders make it difficult to contain Ebola</a>
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<p>Malaria parasites and mosquitoes do not respect country borders, so malaria services must expand to mobile and marginalised populations. Universal access to effective malaria diagnostics and treatment will reduce the malaria burden by decreasing onward transmission.</p>
<h2>Resistance</h2>
<p>One of the biggest threats to eliminating and eradicating malaria is the <a href="https://www.who.int/news-room/fact-sheets/detail/malaria#:%7E:text=Progress%20in%20global%20malaria%20control,to%20insecticides%20among%20Anopheles%20mosquitoes">emergence and spread</a> of insecticide, diagnostic and drug resistance. </p>
<p>Both the malaria vectors and parasites have proved to be very adaptable. They have rapidly developed mechanisms to survive and multiply in the presence of insecticides and antimalarial drugs, respectively. </p>
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Read more:
<a href="https://theconversation.com/some-malaria-parasites-are-evading-detection-tests-causing-an-urgent-threat-to-public-health-177258">Some malaria parasites are evading detection tests, causing an urgent threat to public health</a>
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<p>Insecticide resistance is widespread across the <a href="https://www.bdi.ox.ac.uk/news/tracking-the-spread-of-mosquito-insecticide-resistance-across-africa">African region</a>. It reduces the efficacy of strategies based on suppressing vectors, such as long-lasting insecticide treated nets and indoor residual spraying. </p>
<p>To extend the effective lifespan of the available insecticides, the WHO has provided <a href="http://apps.who.int/iris/bitstream/handle/10665/44768/9789241502801_eng.pdf;jsessionid=233E06F6978781E9163F1479ED99F9F7?sequence=1">new guidance</a> in its handbook for integrated vector management. The handbook highlights the importance of routine entomological surveillance to determine the type of vectors present, changes in vector behaviour and the insecticide susceptibility status of the vector. All this information can guide effective vector suppression if available in good time. </p>
<p>Having the correct diagnostic method and treatment in place also hinges on having a robust surveillance system. The system must be capable of generating efficacy data in near real-time to allow for prompt evidence-based decision-making. The need for this type of <a href="https://www.who.int/news/item/28-05-2021-statement-by-the-malaria-policy-advisory-group-on-the-urgent-need-to-address-the-high-prevalence-of-pfhrp2-3-gene-deletions-in-the-horn-of-africa-and-beyond">routine surveillance</a> has become even more urgent as African malaria parasites have developed mutations that allow them to evade detection by the most widely used rapid diagnostic tests on the continent. These undetected cases will go untreated, potentially sustaining onward transmission. The result will be major increases in malaria cases, severe disease, and potentially death.</p>
<p>Besides becoming invisible to rapid diagnostic tests, <em>P. falciparum</em> parasites in many central and west African countries have become <a href="https://www.npr.org/sections/goatsandsoda/2022/02/06/1077953012/drug-resistant-malaria-is-emerging-in-africa-doctors-are-worried-yet-hopeful">resistant</a> to artemisinins. This is a component of the most widely used antimalarials in Africa, ACTs. The spread of artemisinin-resistant parasites will potentially raise case numbers and deaths, repeating the devastating trend observed when drug-resistant parasites previously emerged. The loss of ACTs would severely set back elimination efforts as there are no novel WHO-approved antimalarials currently available. Efforts are needed to prevent the spread of artemisinin-resistant parasites through strong surveillance and containment responses.</p>
<h2>Climate change</h2>
<p>The impact of climate change is complex, but there are <a href="https://www.un.org/en/chronicle/article/climate-change-and-malaria-complex-relationship#:%7E:text=An%20increase%20in%20temperature%2C%20rainfall,it%20was%20not%20reported%20earlier">suggestions</a> that more places will become malaria risk areas. Mosquitoes will now be able to survive and transmit malaria in these warmer areas. This, in turn, will increase malaria cases, severe illness and deaths in the non-immune communities.</p>
<h2>Positive developments</h2>
<p>In spite of these challenges, there is some light at the end of tunnel. </p>
<p>After years of research there are two new malaria vaccines. The first, <a href="https://www.gsk.com/en-gb/media/press-releases/who-grants-prequalification-to-gsk-s-mosquirix-the-first-and-only-approved-malaria-vaccine/">Mosquirix</a>, has been prequalified for use by the WHO. The second, <a href="https://www.medicalnewstoday.com/articles/malaria-new-vaccine-candidate-shows-promise-in-clinical-trials">R21/Matrix M</a>, has shown promising results in phase 2 clinical trials. </p>
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Read more:
<a href="https://theconversation.com/vaccines-could-be-a-game-changer-in-the-fight-against-malaria-in-africa-193233">Vaccines could be a game-changer in the fight against malaria in Africa</a>
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<p>There are new long-lasting insecticide treated nets and insecticide formulations for vector control. There are also novel strategies for parasite suppression. </p>
<p>Adding these tools to the elimination toolbox will assist Africa get closer to malaria elimination.</p><img src="https://counter.theconversation.com/content/193399/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jaishree Raman is affiliated with the National Institute for Communicable Diseases, the Wits Research Institute for Malaria and UP Institute for Sustainable Malaria Control. She received funding from the South African Research Trust, South African Medical Research Council, Bill and Melinda Gates Foundation, the Global Fund, Clinton Health Access Initiative, National Research Foundation and the National Institute for Communicable Diseases</span></em></p><p class="fine-print"><em><span>Shüné Oliver s affiliated with the National Institute for Communicable Diseases and the Wits Research Institute for Malaria and receives funding from the National Research Foundation, the National Health Laboratory Services Research Trust and the Female Academic Leadership fund. </span></em></p>There are many reasons that malaria is so persistent in Africa. Four of them are poverty, human movement, resistance and climate change.Jaishree Raman, Principal Medical Scientist and Head of Laboratory for Antimalarial Resistance Monitoring and Malaria Operational Research, National Institute for Communicable DiseasesShüné Oliver, Medical scientist, National Institute for Communicable DiseasesLicensed as Creative Commons – attribution, no derivatives.