tag:theconversation.com,2011:/fr/topics/insect-bites-2809/articlesInsect bites – The Conversation2023-12-08T02:55:55Ztag:theconversation.com,2011:article/2189082023-12-08T02:55:55Z2023-12-08T02:55:55ZFire ants are on the march. Here’s what happens when they sting<figure><img src="https://images.theconversation.com/files/564401/original/file-20231207-28-zox765.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C998%2C666&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/red-fire-ant-1211635918">Veronika Kunitsyna/Shutterstock</a></span></figcaption></figure><p>Red imported fire ants are a particularly nasty type of ant because they are aggressive, and inflict painful stings that may be life threatening. That’s in addition to being a serious threat to <a href="https://www.business.qld.gov.au/industries/farms-fishing-forestry/agriculture/biosecurity/animals/invasive/restricted/fire-ant">agriculture and biosecurity</a>. </p>
<p><a href="https://www.dpi.nsw.gov.au/biosecurity/insect-pests/fire-ants">In recent weeks</a>, we heard these ants <a href="https://www.outbreak.gov.au/current-outbreaks/red-imported-fire-ant">had spread</a> from Queensland, south into northern New South Wales.</p>
<p>Although their stings are rare in Australia, they can lead to a serious allergic reaction. Here’s what to do if you’ve been stung.</p>
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<em>
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Read more:
<a href="https://theconversation.com/why-red-fire-ants-and-yellow-crazy-ants-have-given-themselves-a-green-light-to-invade-australia-208479">Why red fire ants and yellow crazy ants have given themselves a green light to invade Australia</a>
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<h2>Which ants are we talking about?</h2>
<p>Red imported fire ants (<em>Solenopsis invicta</em>) are native to South America but have been <a href="https://www.ncbi.nlm.nih.gov/books/NBK470576/">spreading across the world</a> in contaminated soil.</p>
<p><a href="https://www.dpi.nsw.gov.au/biosecurity/insect-pests/fire-ants">The ants</a> are 2-6 millimetres long and are a dark red-brown colour. They live in nests in the ground. </p>
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<iframe width="440" height="260" src="https://www.youtube.com/embed/_XL6QWRHZes?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Here’s what red imported fire ants look like (Biosecurity Queensland).</span></figcaption>
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<p>When a nest is disturbed, hundreds of ants come out and attack. Their jaws lock onto the skin and they arch their body to <a href="https://www.ncbi.nlm.nih.gov/books/NBK470576/">inject venom</a> through a stinger on their abdomen. Each ant stings an average <a href="https://www.ncbi.nlm.nih.gov/books/NBK470576/">seven to eight times</a>.</p>
<p>These ants sting <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8151706/">millions of people</a> a year in the United States.</p>
<p>Anyone who disturbs their nest is at risk of being stung. Even minor disturbances will cause the ants to surface and attack.</p>
<p>Overseas, people have been stung by ants that have <a href="https://pubmed.ncbi.nlm.nih.gov/37355195/">formed rafts</a> during heavy rainfall and flooding.</p>
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<em>
<strong>
Read more:
<a href="https://theconversation.com/from-deadly-jaws-and-enormous-strength-to-mushroom-farming-ant-man-is-only-tapping-into-a-portion-of-the-real-superpowers-of-ants-200530">From deadly jaws and enormous strength to mushroom farming, Ant-Man is only tapping into a portion of the real superpowers of ants</a>
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<h2>What happens when this ant stings you?</h2>
<p>Fortunately, red imported fire ant stings have been uncommon in Australia, and we hope it stays this way.</p>
<p><a href="https://www.ncbi.nlm.nih.gov/books/NBK470576/">Their sting</a> is painful, with a fire-like burning character, and is associated with swelling and redness. Over the following hours or days, sting sites develop blisters or pustules that are itchy and take days to improve. </p>
<p>A person can easily be stung hundreds of times, which can cause a lot of distress.</p>
<h2>What’s the treatment? Do I need to go to hospital?</h2>
<p>Many people with a smaller number of stings can be safely managed at home. <a href="https://www.healthdirect.gov.au/insect-bites-and-stings">Usual treatments</a> <a href="https://www.poisonsinfo.health.qld.gov.au/bites-and-stings/insect-bites-and-stings">include</a>:</p>
<ul>
<li><p>gently washing the area with soap and water</p></li>
<li><p>using cold compresses on red and swollen stings. If you use an ice pack or ice, avoid direct contact with the skin</p></li>
<li><p>taking <a href="https://www.healthdirect.gov.au/antihistamines#:%7E:text=What%20are%20antihistamines%3F-,Antihistamines%20are%20medicines%20that%20you%20can%20take%20to%20treat%20allergies,called%20histamine%20in%20your%20body.">antihistamines</a>, which you can buy from your local pharmacy. </p></li>
</ul>
<p>Do not break the blisters that form at sting sites, and see your local doctor if the stings become more red and painful a few days later, to exclude infection.</p>
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<p>
<em>
<strong>
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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</em>
</p>
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<h2>When to seek medical care</h2>
<p>Uncommonly, red imported fire ant stings can be <a href="https://pubmed.ncbi.nlm.nih.gov/2760357/">life threatening</a>. <a href="https://www.ncbi.nlm.nih.gov/books/NBK470576/">About 2%</a> of people who are stung develop a severe and life-threatening allergic reaction known as anaphylaxis. This has also been <a href="https://pubmed.ncbi.nlm.nih.gov/12064982/">reported</a> in Australia. </p>
<p><a href="https://www.allergy.org.au/patients/insect-allergy-bites-and-stings/allergic-reactions-to-bites-and-stings">Many stinging animals</a> in Australia can cause anaphylaxis, including bees, wasps, and other ants such as <a href="https://www.allergy.org.au/patients/insect-allergy-bites-and-stings/jack-jumper-ant-allergy">jack jumper ants</a>.</p>
<p>People allergic to some wasps may also <a href="https://pubmed.ncbi.nlm.nih.gov/26708389/">be allergic</a> to venom from the red fire ants. </p>
<p>Symptoms of anaphylaxis after being stung by a fire ant are similar to those after being stung by other animals. <a href="https://www.allergy.org.au/patients/about-allergy/anaphylaxis">Symptoms include</a>:</p>
<ul>
<li><p>difficulty talking or breathing</p></li>
<li><p>noisy breathing</p></li>
<li><p>swelling of the face (including lips, eyes or tongue)</p></li>
<li><p>tightness in the throat, with difficulty swallowing</p></li>
<li><p>dizziness</p></li>
<li><p>collapsing. </p></li>
</ul>
<p>There may also be a spreading red rash (hives or welts).</p>
<p>If you have any <a href="https://www.allergy.org.au/patients/about-allergy/anaphylaxis">of these symptoms</a>, seek immediate medical assistance. This may including calling 000. </p>
<p>Rarely, the ant venom can cause other toxic effects, which may be more likely in people who have been stung hundreds of times. So seek medical advice if you have unexplained or unusual symptoms after you’ve been stung.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/ants-bees-and-wasps-the-venomous-australians-with-a-sting-in-their-tails-51024">Ants, bees and wasps: the venomous Australians with a sting in their tails</a>
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<h2>Avoid these ants if you can</h2>
<p>Avoid exposing yourself to imported red fire ants. Report nests to authorities. Do not handle the nests yourself as this is more likely to spread the ants. This is also when you’re most likely to be stung.</p>
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<p><em>If this article raises health concerns for you or for someone you know about insect stings call the <a href="https://www.poisonsinfo.nsw.gov.au">Poisons Information Centre</a> from anywhere in Australia on 131 126. This evidence-based advice is available 24 hours a day. For life-threatening symptoms, call 000.</em></p><img src="https://counter.theconversation.com/content/218908/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Darren Roberts is the Medical Director of the NSW Poisons Information Centre </span></em></p>Most stings can be safely handled at home. But in rare cases, you can get a serious allergic reaction, which needs urgent medical attention.Darren Roberts, Conjoint Associate Professor in clinical pharmacology and toxicology, St Vincent’s Healthcare Clinical Campus, UNSW SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2086392023-07-04T15:11:39Z2023-07-04T15:11:39ZBiting flies are attracted to blue traps – we used AI to work out why<p>Flies which feast on blood – such as tsetse and horse flies – inflict painful bites and spread debilitating diseases among people and animals alike. So a lot of work has gone into designing the most efficient traps to control the populations of these flies.</p>
<p>Biting fly traps tend to be blue, because decades of field research has shown that such flies find this colour especially attractive. But it’s never been clear why these flies find blue to be so irresistible – especially since blue objects are not a common sight in the natural environment.</p>
<p>Scientists have speculated that blue surfaces might look like <a href="https://royalsocietypublishing.org/doi/10.1098/rsbl.2003.0121">shaded places</a> to flies since shadows have a blueish tinge. Tsetse flies in particular seek out such shaded spots to rest in, which might explain their attraction to blue traps. </p>
<p>Another possibility is that blue surfaces might <a href="https://resjournals.onlinelibrary.wiley.com/doi/full/10.1046/j.1365-2915.1999.00163.x">lure hungry flies</a> by providing them with the telltale signs they use to distinguish animals against a background of foliage. According to this theory, a fly might mistake a blue trap for an animal it wishes to bite and feed upon. </p>
<figure class="align-left ">
<img alt="A blue canvas, diamond shaped container is suspended from a tree." src="https://images.theconversation.com/files/535007/original/file-20230630-24873-ovj9iw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/535007/original/file-20230630-24873-ovj9iw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/535007/original/file-20230630-24873-ovj9iw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/535007/original/file-20230630-24873-ovj9iw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/535007/original/file-20230630-24873-ovj9iw.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/535007/original/file-20230630-24873-ovj9iw.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/535007/original/file-20230630-24873-ovj9iw.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A bright blue trap for tsetse flies is suspended from a tree.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/bright-blue-trap-dangerous-tsetse-fly-724357057">Fabian Plock/Shutterstock</a></span>
</figcaption>
</figure>
<p>But assessing these possibilities is especially tricky because flies perceive colour differently to people. Humans perceive colour using the responses of three kinds of light-detecting photoreceptor in the retina which are broadly sensitive to blue, green and red wavelengths of light.</p>
<p>But most “higher flies” – such as tsetse and horseflies – have five kinds of photoreceptor sensitive to UV, blue and green wavelengths. So, a blue trap won’t look the same to a fly as it does to the human who designed it.</p>
<h2>From flies to AI…</h2>
<p>In <a href="https://royalsocietypublishing.org/doi/10.1098/rspb.2023.0463#d1e1574">our study</a>, we tackled the problem by using artificial intelligence (AI). We used artificial neural networks which are a form of machine learning inspired by the structure of real nervous systems. Artificial neural networks learn by modifying the strengths of connections between a network of artificial neurons.</p>
<p>We fed these networks with the photoreceptor signals that a fly would experience when looking at animals or foliage backgrounds, both in light and in shade. We then trained the networks to distinguish animals from leaves, and shaded from unshaded objects, using only that visual information.</p>
<p>The trained networks would find the most efficient way of processing the visual signals, which we expected to share properties with the mechanisms that have evolved in real flies’ nervous systems. We then investigated whether the artificial neural networks classified blue traps as animals or as shaded surfaces.</p>
<h2>Blueness or brightness?</h2>
<p>After training, our neural networks could easily distinguish animals from leaf backgrounds, and shaded from unshaded stimuli, using the sensory information available to a fly. However, what surprised us was that they solved these problems in completely different ways.</p>
<p>The networks identified shade using brightness and not colour – quite simply, the darker a stimulus appeared, the more likely it was to be classified as shaded. Meanwhile, animals were identified using the relative strength of blue and green photoreceptor signals. Relatively greater blue compared to green signals indicated that a stimulus was probably an animal rather than a leaf, and vice versa.</p>
<p>The implications of this became clear when we fed these networks the visual signals caused by blue traps. The blue traps were never mistaken for shaded surfaces, but they were commonly misclassified as animals.</p>
<figure class="align-center ">
<img alt="A close up of an insect with huge blue/green eyes" src="https://images.theconversation.com/files/535038/original/file-20230630-13700-zuvny9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/535038/original/file-20230630-13700-zuvny9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/535038/original/file-20230630-13700-zuvny9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/535038/original/file-20230630-13700-zuvny9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/535038/original/file-20230630-13700-zuvny9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/535038/original/file-20230630-13700-zuvny9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/535038/original/file-20230630-13700-zuvny9.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 horse fly (<em>Hybomitra epistates</em>) can inflict painful bites upon people and livestock.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/horse-fly-hybomitra-epistates-portrait-1773555527">Mircea Costina/Shutterstock</a></span>
</figcaption>
</figure>
<p>Of course, artificial neural networks are not real flies, nor exact models of a fly’s nervous system. But they do show us the most efficient way of processing a fly’s visual signals to identify natural stimuli. And we expect evolution to have taken advantage of similar principles in real fly nervous systems.</p>
<p>The best way to identify shade using the visual information a fly has is through brightness and not blueness. Meanwhile, the best way of identifying animals was, somewhat counterintuitively, using blueness. Such a mechanism is very strongly stimulated by blue traps, explaining why they prove such a powerful lure for hungry flies. Further evidence for this idea comes from field studies which show that tsetse landing on coloured traps are <a href="https://resjournals.onlinelibrary.wiley.com/doi/abs/10.1111/j.1365-3032.1990.tb00519.x">relatively starved</a>.</p>
<p>If we can understand the sensory signals and behaviour that cause flies to be caught in traps, we can engineer traps to more efficiently exploit those mechanisms and more effectively control the flies. We’ve already had <a href="https://journals.plos.org/plosntds/article?id=10.1371%2Fjournal.pntd.0007905#:%7E:text=Tsetse%20can%20be%20controlled%20using%20insecticide-treated%20fabric%20targets%2C,these%20fabrics%20to%20be%20more%20attractive%20to%20tsetse.">some success</a> in doing this for tsetse flies.</p>
<p>More effective traps will help minimise the impacts of those flies on health and welfare of people and animals. They could help prevent the damaging effects of biting flies on livestock, help in the fight against dangerous fly-borne diseases such as <a href="https://www.who.int/news-room/fact-sheets/detail/trypanosomiasis-human-african-(sleeping-sickness)">sleeping sickness</a>, and protect us and animals from fly attacks in general.</p><img src="https://counter.theconversation.com/content/208639/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Roger Santer has received funding from the Knowledge Economy Skills Scholarships program, and from the Centre for International Development Research at Aberystwyth (CIDRA). </span></em></p>New research on what attracts blood-feasting flies to blue objects could help minimise the impacts of those insects on people and animals.Roger Santer, Lecturer in Zoology, Aberystwyth 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>
<figure class="align-center ">
<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">
<figcaption>
<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>
</figcaption>
</figure>
<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/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>
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<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>
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<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/1926192022-11-08T09:04:59Z2022-11-08T09:04:59ZA dumpsite is no place for a child: study shows Nigeria’s young waste pickers are at risk<figure><img src="https://images.theconversation.com/files/491263/original/file-20221024-1609-y8vdtg.jpg?ixlib=rb-1.1.0&rect=7%2C0%2C2588%2C1715&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Children are among waste pickers exposed to hazards while working at the Olusosun landfill. Photo by: Lionel Healing/AFP.</span> <span class="attribution"><a class="source" href="https://www.gettyimages.com/detail/news-photo/people-sift-through-rubbish-at-a-dump-17-april-2007-in-news-photo/73905533?phrase=olusosun%20dumpsite%20Lagos&adppopup=true">from www,gettyimages.com</a></span></figcaption></figure><p>The Olusosun landfill sprawls across 100 acres (40ha) in Nigeria’s largest city, Lagos. Initially situated at the outskirts of the city, it is now at the city’s centre due to urban encroachment. Olusosun is often described as <a href="https://link.springer.com/article/10.1007/s12011-021-02758-3">Nigeria’s biggest landfill</a>; it receives over one million tonnes of <a href="https://owlcation.com/stem/15-of-the-Worlds-Largest-Landfills">waste</a> annually. Most of this is electronic waste (such as lamps, televisions and laptops), municipal solid waste and construction waste.</p>
<p>Access to the dumpsite is not restricted. Waste pickers can go in and look for recyclable materials that can be resold. In most Nigerian cities, waste picking represents a vital survival strategy for the <a href="https://www.ijern.com/journal/March-2014/26.pdf">poor</a>.</p>
<p>It’s not only adults who operate as waste pickers. As we outline in our recent <a href="https://thescipub.com/abstract/10.3844/ajessp.2022.69.80">study</a>, children are also working at Olusosun. </p>
<p>We surveyed 150 of these child waste pickers; most were boys aged between 13 and 17. More than half (58.7%) of the children were not attending school. They worked at the dumpsite daily for social and economic reasons and their labour was physically taxing. They reported being bitten by insects and snakes. They slipped and sometimes fell. Many suffered from chronic headaches. For this they earned between N500 (US$1.20) and N1,600 (US$3.85) a day. </p>
<p>The use of a child for forced or <a href="https://www.scirp.org/journal/paperinformation.aspx?paperid=64999">exploitative labour</a> under section 28 (1) (a) of the Child’s Rights Act is an offence punishable with a fine or imprisonment. But in the informal sector of urban areas, Nigeria’s government has not made serious efforts to enforce this law to protect children.</p>
<p>A concerted effort is needed by government, civil society, and international organisations to eradicate waste picking by children. Financial aid could be offered to the children’s families so that they don’t feel they have no option but to let children work. And free, compulsory primary and secondary education is key to keeping children in the classroom rather than working.</p>
<h2>Huge health and safety risks</h2>
<p>Access to Olusosun landfill is unregulated, but there are informal systems in place to manage who can and cannot engage in waste picking. Our <a href="https://doi.org/10.3844/ajessp.2022.69.80">survey</a> confirmed that before any person could pick waste on this site, they had to register with an association. Unregistered people were not allowed to work on the site and if they did without permission, there would be a quarrel. </p>
<p>An informal association formed by the operators oversees the registration process. It is funded by membership fees and only registers adults. But once they are registered, those adults can hire children to do the work for them. They do this, we were told, to keep their costs low because they could pay children less than they would pay adults.</p>
<p>Information we obtained showed that child waste pickers’ minimum daily income was N500 (US$1.20); the maximum was N1,600 (US$3.85). The average daily revenue was N1,180 (US$2.84) – more than N30,000 (about US$72.20) per month. Although this amount is higher than the <a href="https://doi.org/10.3844/ajessp.2022.69.80">national minimum monthly wage</a> (N30,000) in the public sector, the work and the environment are hazardous and detrimental to the children’s health.</p>
<p>Children usually sorted the waste manually, with no protective equipment like gloves and face masks. They operated in an unsheltered environment regardless of conditions like rain, hot sun and cold weather. These conditions had resulted in gastrointestinal illnesses, skin diseases, stings and bites from insects. Many talked about suffering regular headaches.</p>
<p>Child waste pickers were also at risk of being pricked by sharp objects such as syringes, needles, surgical blades and broken bottles.</p>
<p>Despite all these hazards, the children continued working at the landfill because of chronic poverty. Some of the children’s parents were waste
pickers themselves. Many came from areas without <a href="https://www.premiumtimesng.com/news/more-news/469581-less-than-40-of-lagos-residents-have-access-to-water-governor.html">potable water</a>, sanitation facilities or basic healthcare services. </p>
<h1>Recommendations</h1>
<p>In addressing the use of children for forced or exploitative labour, integrated approaches have
<a href="https://assets.publishing.service.gov.uk/media/5984577fe5274a1707000067/105-Interventions-on-Child-Labour-in-South-Asia.pdf">demonstrated</a> the most success in South Asian countries. (Afghanistan is an important exception.) These approaches can include, for example, conditional cash transfers combined with interventions such as providing education and healthcare services. </p>
<p>Thus, a pragmatic regulatory framework should be developed whereby different actors (government, civil society and international organisations) focus on eliminating the practice of waste picking by children. Such efforts require strong political backing and financial support. </p>
<p>Such a regulatory framework should also make provision for financial aid to the children’s parents through a direct assistance programme. </p>
<p>There is a need for a well-thought-out plan by the government to introduce free and compulsory primary and secondary education for every child. Making education compulsory, especially at the secondary level, is a way to keep children learning and, ideally, setting themselves up for safe, decently-paid future work.</p><img src="https://counter.theconversation.com/content/192619/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Amos Oluwole Taiwo 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>Employing children as waste pickers lowers costs but exposes them to hazards.Amos Oluwole Taiwo, Lecturer, Department of Urban and Regional Planning, Olabisi Onabanjo University, Ago-Iwoye, Ogun State, Nigeria, Olabisi Onabanjo UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1487222020-12-28T21:42:20Z2020-12-28T21:42:20ZBzzz, slap! How to treat insect bites (home remedies included)<figure><img src="https://images.theconversation.com/files/373750/original/file-20201209-17-7qzomc.jpg?ixlib=rb-1.1.0&rect=0%2C7%2C1000%2C657&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/protecting-mosquito-on-camping-by-river-1485041048">Shutterstock</a></span></figcaption></figure><p>It’s the holidays and we’re spending more time outdoors. This means we’re exposed to the more annoying and painful aspects of summer — insect bites and stings. </p>
<p>There are plenty of products at the local pharmacy to treat these. Some treat the initial bite or sting, others the itchy aftermath.</p>
<p>What about natural remedies? Few studies have actually examined them. But if they work for you, and don’t irritate already inflamed skin, there’s likely no harm in continuing.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/buzz-buzz-slap-why-flies-can-be-so-annoying-52296">Buzz, buzz, slap! Why flies can be so annoying</a>
</strong>
</em>
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<h2>Why do insects bite and sting?</h2>
<p>When insects bite and sting, they are either defending themselves or need something from us (like blood).</p>
<p>Whatever the motivation, it can leave us with a painful or itchy reaction, sometimes a severe allergic reaction, or even a debilitating disease.</p>
<p>While insects sometimes get a bad rap, there are relatively few that actually pose a serious threat to our health.</p>
<p><strong>Flies, mosquitoes</strong></p>
<p>Many types of flies, especially mosquitoes, bite. In most instances, they need blood for nutrition or the development of eggs. The method of “biting” can vary between the different types of flies. While mosquitoes inject a needle-like tube to suck our blood, others chew or rasp away at our skin.</p>
<p>While researchers have studied what happens when <a href="https://journals.lww.com/itch/Fulltext/2019/03000/Beat_the_bite__pathophysiology_and_management_of.1.aspx">mosquitoes bite</a>, there is still much to learn about how to treat the bites.</p>
<p>So, avoiding mosquito bites is especially important given some can <a href="https://theconversation.com/explainer-what-is-ross-river-virus-24630">transmit pathogens that make us sick</a>.</p>
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<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>
</strong>
</em>
</p>
<hr>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/372798/original/file-20201203-15-1hz7tea.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/372798/original/file-20201203-15-1hz7tea.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/372798/original/file-20201203-15-1hz7tea.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/372798/original/file-20201203-15-1hz7tea.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/372798/original/file-20201203-15-1hz7tea.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/372798/original/file-20201203-15-1hz7tea.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/372798/original/file-20201203-15-1hz7tea.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">We still have lots to learn about treating mosquito bites.</span>
<span class="attribution"><span class="source">A/Prof Cameron Webb</span></span>
</figcaption>
</figure>
<p><strong>Fleas, lice, mites and ticks</strong></p>
<p>There are lots of other insects (such as bed bugs, fleas, lice) and other arthropods (such as mites, ticks) <a href="https://healthinfonet.ecu.edu.au/key-resources/resources/30905/?title=Arthropod%20pests%20of%20public%20health%20significance%20in%20Australia">that bite</a>. </p>
<p>But it is difficult to determine which insect has bitten us <a href="https://www.mdpi.com/2075-4418/10/5/308/htm">based on the bite reaction alone</a>. This is generally because different people react in different ways to the <a href="https://theconversation.com/curious-kids-when-we-get-bitten-by-a-mosquito-why-does-it-itch-so-much-93347">saliva injected</a> as they start to suck our blood.</p>
<p><strong>Bees, wasps, ants</strong></p>
<p>Then there are stinging insects, such as bees, wasps and ants. These are typically just defending themselves.</p>
<p>But as well as being painful, the venom they inject when they sting can cause <a href="https://www.allergy.org.au/patients/insect-allergy-bites-and-stings/allergic-reactions-to-bites-and-stings">potentially severe allergic reactions</a>.</p>
<h2>How do you best treat a sting or bite?</h2>
<p>If you suffer potentially severe allergic reactions from <a href="https://www.sciencedirect.com/science/article/abs/pii/S1081120610612598">bites or stings</a>, immediately seek appropriate medical treatment. But for many other people, it is the initial painful reaction and itchy aftermath that require attention.</p>
<p>Despite how common insect bites can be, there is <a href="https://www.bmj.com/content/370/bmj.m2856">surprisingly little formal research</a> into how best to treat them. Most of the research is focused on insect-borne diseases.</p>
<p>Even for recommended treatments, <a href="https://dtb.bmj.com/content/50/4/45.abstract">there is little evidence</a> they actually work. Instead, recommendations are based on expert opinion and clinical experience.</p>
<p>For instance, heath authorities promote <a href="https://www.healthdirect.gov.au/insect-bites-and-stings">some general advice</a> on treating insect bites and stings. This includes using pain relief medication (such as paracetamol or ibuprofen). They also advise applying a cold compress (such as a cold pack, ice, or damp cloth soaked in cold water) to the site of the sting or bite to help reduce the inflammation and to ease some of the discomfort.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/373745/original/file-20201209-15-v7t8cg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Refreshing red drink in glass with ice cubes and lemon" src="https://images.theconversation.com/files/373745/original/file-20201209-15-v7t8cg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/373745/original/file-20201209-15-v7t8cg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/373745/original/file-20201209-15-v7t8cg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/373745/original/file-20201209-15-v7t8cg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/373745/original/file-20201209-15-v7t8cg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/373745/original/file-20201209-15-v7t8cg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/373745/original/file-20201209-15-v7t8cg.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">Ice cubes aren’t just for summer cocktails. They can help reduce inflammation from insect bites and stings.</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/top-view-spritz-aperitif-aperol-cocktail-279703073">Shutterstock</a></span>
</figcaption>
</figure>
<p>There is also specific advice for <a href="https://www.allergy.org.au/patients/insect-allergy-bites-and-stings/allergic-reactions-to-bites-and-stings">dealing with stings</a> and removing <a href="https://theconversation.com/tackling-the-tricky-task-of-tick-removal-26306">ticks</a>.</p>
<p>However, if you do nothing, the discomfort of the bite or sting will eventually fade after a few days. The body quickly recovers, just as it would for a cut or bruise.</p>
<p>If you’re still in pain for more than a couple of days, or there are signs of an allergic reaction, seek medical assistance.</p>
<h2>What about the itch?</h2>
<p>Once the initial pain has started to fade, the itch starts. That’s because the body is reacting to the <a href="https://www.frontiersin.org/articles/10.3389/fcimb.2020.00407/full">saliva injected</a> when insects bite.</p>
<p>For many people, this is incredibly frustrating and it is all too easy to get trapped in a cycle of itching and scratching.</p>
<p>In some cases, medications, such as <a href="https://www.healthdirect.gov.au/medicines/brand/amt,1159191000168108/hydrocortisone-pharmacy-action">corticosteroid</a> creams or <a href="https://emj.bmj.com/content/23/9/721.2">antihistamines</a> could help alleviate the itchiness. You can buy these from the pharmacy.</p>
<p>Then there’s <a href="https://www.healthline.com/health/calamine-lotion-uses">calamine lotion</a>, a mainstay in many Australian homes used to treat the itchiness caused by insect bites. But there are <a href="https://www.sciencedirect.com/science/article/pii/S1080603206702757">few studies</a> that demonstrate it works.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/are-itchier-insect-bites-more-likely-to-make-us-sick-61422">Are itchier insect bites more likely to make us sick?</a>
</strong>
</em>
</p>
<hr>
<h2>Do any home remedies work?</h2>
<p>If you’re looking for a home remedy to treat insect bites and the itchiness that comes with it, a quick internet search will keep you busy for days. </p>
<p><a href="https://www.healthline.com/health/outdoor-health/home-remedies-for-mosquito-bites">Potential home remedies</a> include: tea bags, banana, tea tree or other essential oils, a paste of baking soda, vinegar, aloe vera, oatmeal, honey and even onion.</p>
<p>There is little evidence any of these work. But not many have actually been scientifically evaluated. </p>
<p>Tea tree oil is one of the few. While it is said to help <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/j.1365-4632.2012.05654.x">treat skin reactions</a>, the oil itself can cause skin reactions <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/cod.12591">if not used as directed</a>.</p>
<p>However, if a home remedy works for you, and it’s not causing additional irritation, there’s no harm in using it if you’re getting some relief. </p>
<p>With so much uncertainty about how to treat insect bites and stings, perhaps it is best if we avoid exposure in the first place. There are <a href="https://theconversation.com/the-best-and-worst-ways-to-beat-mosquito-bites-70274">plenty of insect repellents</a> available at your local pharmacy or supermarket that do this safely and effectively.</p><img src="https://counter.theconversation.com/content/148722/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>Summer can bring out the bugs. Here’s what to do if you miss a spot when applying insect repellent.Cameron Webb, Clinical Associate Professor and Principal Hospital Scientist, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/680252016-11-02T09:17:15Z2016-11-02T09:17:15ZScientists turn one pathogen against another in fight against dengue and Zika<figure><img src="https://images.theconversation.com/files/144110/original/image-20161101-11456-2s4w5m.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Aedes_aegypti.jpg">Muhammad Mahdi Karim</a></span></figcaption></figure><p>Mosquitoes have been described as the most dangerous animals in the world due to their role in spreading diseases such as <a href="http://www.who.int/features/factfiles/malaria/en/">malaria</a>, <a href="http://www.who.int/mediacentre/factsheets/fs117/en/">dengue</a>, <a href="http://www.who.int/mediacentre/factsheets/fs327/en/">chikugunya</a> and <a href="http://www.who.int/mediacentre/factsheets/fs100/en/">yellow fever</a>. Hundreds of millions of people are infected every year, leading to <a href="http://www.who.int/features/factfiles/malaria/en/">many hundreds of thousands of deaths</a>.</p>
<p>One of the biggest concerns this year has been the rapid spread of <a href="http://www.who.int/mediacentre/factsheets/zika/en/">Zika</a>, another virus in the same family as dengue and the yellow fever viruses. There is no vaccine available that is able to protect people from Zika infection at present, and no known cure. So the challenge is to prevent the means of infection: the bite of the mosquito, <em>Aedes aegypti</em>.</p>
<p>Unlike other species of mosquito that transmit the malaria parasite, <em>Aedes</em> mosquitoes bite during the day, which means sleeping under a net offers little protection. Insecticides have been effective but resistance develops rapidly, and public health programmes that target and remove mosquito breeding sites are expected to be difficult to sustain. This has led to a sophisticated new approach that uses one species of parasite to prevent the spread of another.</p>
<h2>Bacteria vs virus</h2>
<p>The parasites in question belong to a group of bacteria called <a href="http://www.eliminatedengue.com/our-research/wolbachia">Wolbachia</a>. These naturally infect a great number of insect species, in which they inhabit tissues including the insect’s ovaries. From here they infect the developing eggs, and so are passed on to the next generation. Although it’s only female insects that can pass the bacteria on to their offspring, the bacteria can reduce the reproductive capability of both male and female hosts. Depending upon the species of Wolbachia, this can lead to sterility, or to swing the sex ratio of offspring in favour of females – which in turn means Wolbachia will spread more rapidly through the insect population through successive generations of infected eggs.</p>
<p>However, Wolbachia infection is not all bad news for insects: there is evidence that Wolbachia also prevents other pathogens from developing in host insects. </p>
<p>For several years, an Australian research group led by <a href="https://www.monash.edu/science/schools/biological-sciences/staff2/oneill">Scott O’Neill</a> has taken advantage of this as a strategy to control the spread of dengue viruses. But in order to use Wolbachia to prevent other pathogens from infecting <em>Aedes</em> mosquitoes, first they had to overcome a big hurdle because <em>Aedes</em> are not naturally infected with Wolbachia. </p>
<p>Using very fine needles, they were able to inject Wolbachia from other insects into newly laid <em>Aedes</em> eggs. The bacteria survived inside the mosquitoes that hatched from the eggs, and began to spread naturally through further generations of their lab mosquito colony. When those mosquitoes infected with Wolbachia were subsequently infected with dengue, the dengue virus was not able to replicate and spread to the mosquito’s salivary glands – and so the mosquitoes could not transmit dengue.</p>
<p><a href="http://www.cell.com/cell/abstract/S0092-8674(09)01500-1?_returnURL=http%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0092867409015001%3Fshowall%3Dtrue">Subsequent research</a> has demonstrated that the same technique using Wolbachia also reduces the ability of <em>Aedes</em> mosquitoes to transmit the viruses that cause yellow fever, chikungunya and Zika – and there is some evidence that it can inhibit transmission of the malaria parasite in other mosquito species. The mechanism by which Wolbachia infection does this is not clear, but it’s likely that it involves a change to the mosquito’s immune system.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/144107/original/image-20161101-15814-3cic7w.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/144107/original/image-20161101-15814-3cic7w.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/144107/original/image-20161101-15814-3cic7w.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=246&fit=crop&dpr=1 600w, https://images.theconversation.com/files/144107/original/image-20161101-15814-3cic7w.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=246&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/144107/original/image-20161101-15814-3cic7w.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=246&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/144107/original/image-20161101-15814-3cic7w.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=309&fit=crop&dpr=1 754w, https://images.theconversation.com/files/144107/original/image-20161101-15814-3cic7w.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=309&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/144107/original/image-20161101-15814-3cic7w.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=309&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Map showing the global distribution of the <em>Aedes aegypti</em> mosquito which spreads dengue and other diseases.</span>
<span class="attribution"><a class="source" href="https://elifesciences.org/content/4/e08347">Moritz UG Kraemer/eLife</a></span>
</figcaption>
</figure>
<h2>Weaponising mosquitoes</h2>
<p>Unlike the viruses, Wolbachia bacteria are too big to pass through the mosquito’s salivary duct when she bites a human, so there’s no chance that Wolbachia-infected mosquitoes can spread Wolbachia to humans – indeed, Wolbachia is not dangerous to humans. Stringent independent risk assessments have concluded that these mosquitoes were of negligible risk to humans or the environment, so trial releases of these mosquitoes have now taken place in Australia. By breeding with wild <em>Aedes</em>, the infected mosquitoes have rapidly spread Wolbachia throughout the population. The <a href="http://www.eliminatedengue.com/program">Eliminate Dengue</a> project has now also released mosquitoes in Indonesia, Vietnam, Colombia and Brazil.</p>
<p>In Brazil, <a href="http://www.eliminatedengue.com/progress/index/article/739">the positive results</a> from two pilot releases of Wolbachia-carrying mosquitoes have led to plans to expand the programme across the Rio de Janeiro and Niterói regions and monitor the effects on mosquito-borne viral infections. Facilities there are capable of producing 10m Wolbachia-infected <em>Aedes</em> eggs for release every week.</p>
<p>In the US, the <a href="http://mosquitomate.com/science-research/">Mosquito Mate</a> project is using a similar technique but instead aims to reduce the number of biting mosquitoes in an area rather than preventing the spread of disease. Using a different species of Wolbachia that causes sterility in the Asian tiger mosquito (<em>Aedes albopictus</em>), the project has released Wolbachia-carrying male mosquitoes which mate with wild females. As no fertile eggs result, the mosquito population declines. However, unlike the Eliminate Dengue strategy, this approach requires continual releases of mosquitoes because this strain of Wolbachia cannot spread naturally within the mosquito population. </p>
<p>Because Wolbachia-carrying mosquitoes are regarded as biopesticides, Mosquito Mate quickly got regulatory approval by the US Environmental Protection Agency. This is in contrast to the experience of firms such as <a href="http://www.oxitec.com/">Oxitec</a> which use genetically modified male mosquitoes that are sterile.</p>
<p>It may take several years to determine whether either of these strategies actually reduces or even eliminates the spread of mosquito-borne viral diseases – but if successful the implications for the millions affected by these diseases worldwide are enormous.</p><img src="https://counter.theconversation.com/content/68025/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Hilary Hurd 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>There’s a new weapon against mosquitoes that spreads diseases such as dengue and yellow fever – more mosquitoes.Hilary Hurd, Emeritus Professor of Parasitology, Keele UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/509632016-01-10T19:16:23Z2016-01-10T19:16:23ZAre Australian snakes the deadliest in the world? Not even close<figure><img src="https://images.theconversation.com/files/107486/original/image-20160107-14020-5z2o2c.png?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Is Australia really the most lethal nation on earth when it comes down to it?</span> <span class="attribution"><span class="source">The Conversation</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>Many Australians pride themselves on the belief that, of all the countries in the world, their snakes, spiders, jellyfish, centipedes, fish, ticks, bees and ants are the worst. And it’s easy to believe they’re right.</p>
<p>After all, there’s <a href="http://www.ncbi.nlm.nih.gov/pubmed/524395">a 37-year-old list</a> that says that 21 of the 25 most toxic snakes in the world are all from Australia. And aren’t funnel-web spiders, box jellyfish, stonefish and cone snails all dead-set killers? </p>
<p>But is Australia really the most lethal nation on earth when it comes down to it? Actually, no, it’s not. And the reason is simple. </p>
<h2>A matter of perspective</h2>
<p>It’s useless to measure how dangerous something is based solely on laboratory lethality tests. Venom toxicity and the number of mice killed with a snake’s average venom yield, for instance, are interesting only from an academic perspective. </p>
<p>If you happen to be one of <a href="https://en.wikipedia.org/wiki/Epidemiology_of_snakebites">around 100,000 people</a> who die of snake bites around the world in any given year, such facts are irrelevant. The same goes for just about any other venomous creature we might like to proudly declare as the planet’s most lethal. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/107332/original/image-20160105-28969-1l0pl0j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/107332/original/image-20160105-28969-1l0pl0j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/107332/original/image-20160105-28969-1l0pl0j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/107332/original/image-20160105-28969-1l0pl0j.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/107332/original/image-20160105-28969-1l0pl0j.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/107332/original/image-20160105-28969-1l0pl0j.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/107332/original/image-20160105-28969-1l0pl0j.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 Eastern Brown Snake (<em>Pseudonaja textilis</em>) and its relatives cause most of the bites and fatalities in Australia.</span>
<span class="attribution"><span class="source">David Williams</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>While Australia has spiders, jellyfish and other animals with lethal venom, the reality is that bites and deaths are rare. In other words, despite very toxic venoms, these creatures don’t bite enough people to cause major problems. Even when they do bite, it’s rare for snakes to inject venom (or “envenom”), less than 450 of 3,000 snakebite cases a year, for example. Death is even rarer (two to three cases a year). </p>
<p>Animals that cause the greatest burden of human suffering and death are the ones we need to be most worried about, and from that perspective, the most dangerous are not Australian. </p>
<p>Consider snakes, one of the most feared groups of venomous animals in the world. If we want to know which snakes are the most dangerous, we should consider the global, rather than individual impact. That view shows three groups of vipers that collectively span almost all of the tropical developing world – and have a huge impact on human health – best deserve the title of <em>the world’s most dangerous</em>.</p>
<h2>Meet the carpet viper</h2>
<p>Perhaps the most dangerous of these three genera is a diverse group of small, seemingly innocuous vipers that range from Sri Lanka and India, across the Middle East and through a huge part of the northern half of Africa. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/105364/original/image-20151211-8297-39c4q6.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/105364/original/image-20151211-8297-39c4q6.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/105364/original/image-20151211-8297-39c4q6.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/105364/original/image-20151211-8297-39c4q6.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/105364/original/image-20151211-8297-39c4q6.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/105364/original/image-20151211-8297-39c4q6.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/105364/original/image-20151211-8297-39c4q6.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">West African carpet viper (<em>Echis ocellatus</em>) from Togo – member of a genus of small vipers that are the world’s most dangerous snakes.</span>
<span class="attribution"><span class="source">David Williams</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>These snakes got their name from the patterns that adorn their bodies. They are small- to medium-sized vipers believed to injure and kill more people each year than any other species in the world. Yet they don’t make the list of most toxic snakes mentioned above at all. </p>
<p><a href="http://www.ncbi.nlm.nih.gov/pubmed/22851309">In just one hospital</a> in Nigeria’s north-eastern Gombe State, 5,367 victims of carpet viper envenoming were treated over a two-year period. But for the use of an effective antivenom, the fatality rate may have been as high as 35% to 45%. That’s more cases at one hospital in two years than all the recorded cases throughout Australia in ten. </p>
<p>Their huge range across a vast swathe of the rural tropics brings carpet vipers into contact with hundreds of thousands of people each year. And while nobody has a tally of just how many lives they affect, international experts all agree that when it comes to the most dangerous snake, these vipers have no competition. </p>
<h2>Russell’s viper</h2>
<p>In Pakistan, India and Sri Lanka, carpet vipers give way to the larger Russell’s viper (<em>Daboia russelii</em>). </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/105363/original/image-20151211-8314-1qqw4l0.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/105363/original/image-20151211-8314-1qqw4l0.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/105363/original/image-20151211-8314-1qqw4l0.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/105363/original/image-20151211-8314-1qqw4l0.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/105363/original/image-20151211-8314-1qqw4l0.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/105363/original/image-20151211-8314-1qqw4l0.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/105363/original/image-20151211-8314-1qqw4l0.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 Russell’s viper (<em>Daboia russelii</em>) arguably the most dangerous snake in Asia with a potent cocktail of destructive toxins in its venom.</span>
<span class="attribution"><span class="source">David Williams</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>This pugnacious viper lurks in fields, rice paddies and farmland from Pakistan through India, Nepal, Sri Lanka, Bangladesh, Myanmar, Thailand and Cambodia, as well as Taiwan and southern China. There’s a distinct, disjoined population of an equally dangerous sister species (<em>Daboia siamensis</em>) in eastern Java and the lesser Sundas in Indonesia.</p>
<p>Like the victims of carpet vipers, those bitten by these snakes bleed uncontrollably and often fatally. At the same time, local tissue destruction and necrosis, acute kidney injury, neurotoxic paralysis, shock, and cardiac arrhythmia can produce a terrifying clinical picture that can very quickly lead to death. </p>
<h2>Lancehead pit vipers</h2>
<p>Latin America, from Mexico to Argentina, is home to more than 40 species in the genus <em>Bothrops</em>, lancehead pit vipers. Collectively, this very diverse group is responsible for many of the estimated 150,000 or more cases of venomous snakebites in Central and South America each year. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/105369/original/image-20151211-8329-fhie1h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/105369/original/image-20151211-8329-fhie1h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/105369/original/image-20151211-8329-fhie1h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/105369/original/image-20151211-8329-fhie1h.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/105369/original/image-20151211-8329-fhie1h.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/105369/original/image-20151211-8329-fhie1h.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/105369/original/image-20151211-8329-fhie1h.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">Venezuelan lancehead (<em>Bothrops venezuelensis</em>) one of a large, widely distributed genus of dangerous pit vipers that cause enormous misery in Latin America.</span>
<span class="attribution"><span class="source">David Williams</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Lancehead bites produce devastating local tissue injury with oedema (or fluid retention), bruising, skin and muscle necrosis and fluid-filled blisters. Permanent disability including amputation is common. </p>
<p>Systemic effects involving stopping the ability of blood to clot, platelet destruction, shock, acute kidney injury and thrombosis present doctors with a complex medical emergency that – even with the best care available in a modern hospital – can still ultimately prove fatal. </p>
<p>Since many cases occur in rural areas, away from good medical care, poor outcomes are common.</p>
<p>Within Australia, the low mortality from snakebite (and other types of venomous injury) is very much the product of decades of research and excellent clinical care, not to mention safe and effective antivenoms. </p>
<p>It’s the lack of these same attributes elsewhere in the world that renders snakebites such a potentially life-changing (if not, life-ending) public health issue. </p>
<p><em>This article is part of our series <a href="https://theconversation.com/au/topics/deadly-australia">Deadly Australia</a>. Stay tuned for more pieces on the topic in the coming days.</em></p>
<hr>
<p><em>David will be on hand for an Author Q&A between 11am and noon AEDT on Tuesday, January 12, 2016. Post your questions in the comments section below.</em></p><img src="https://counter.theconversation.com/content/50963/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>David Williams receives funding from CSL Limited, the National Health and Medical Research Council and the government of Papua New Guinea. He is affiliated with the Global Snakebite Initiative Limited, a not-for-profit advocacy organization, and is an employee of the University of Melbourne. </span></em></p>There’s a simple reason why Australia isn’t the most lethal nation in the world.David Williams, Head, Charles Campbell Toxinology Centre at the University of Papua New Guinea & Australian Venom Research Unit, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/334572014-10-27T19:07:34Z2014-10-27T19:07:34ZSniffing out new repellents: why mozzies can’t stand the DEET<figure><img src="https://images.theconversation.com/files/62853/original/c7f2qfkh-1414386093.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Someone didn't put on the DEET. This is the Yellow Fever mosquito _Aedes aegypti_.</span> <span class="attribution"><span class="source">Stephen Doggett/Pathology West - ICPMR Westmead</span>, <span class="license">Author provided</span></span></figcaption></figure><p>The smell of mozzie repellent is as much a part of summer as barbecues and the cricket. Despite supermarket and pharmacy shelves overflowing with insect repellents, there are actually only a few active ingredients to be found across the different formulations. </p>
<p>The most widespread of these is N,N-Diethyl-meta-toluamide, commonly known as <a href="http://www2.epa.gov/insect-repellents/deet">DEET</a>, and thanks to <a href="http://www.pnas.org/cgi/doi/10.1073/pnas.1417244111">research published</a> in the Proceedings of the National Academy of Sciences today, we now know exactly why mosquitoes find it so repulsive.</p>
<p>To a mosquito, DEET makes you smell awful.</p>
<p>Knowing how repellents work is particularly important as there are around 5,000 cases of disease caused by the mosquito-borne <a href="https://theconversation.com/explainer-what-is-ross-river-virus-24630">Ross River virus</a> every year in Australia. Some regions are also at risk of more serious pathogens such as <a href="https://theconversation.com/explainer-what-is-dengue-fever-8571">dengue</a> and <a href="http://www.plosntds.org/article/info%3Adoi%2F10.1371%2Fjournal.pntd.0002656">Murray Valley encephalitis</a> viruses.</p>
<p>While <a href="http://www.bioone.org/doi/abs/10.2987/10-6038.1">control programs</a> in some parts of Australia may help reduce the activity of mosquitoes, for most of us, the first line of defence against these biting pests will be <a href="https://theconversation.com/aussies-vs-mozzies-a-users-guide-to-repellents-10964">insect repellents</a>. We know these products work, but not <em>exactly</em> how they work. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/62787/original/czfcgdg3-1414369925.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/62787/original/czfcgdg3-1414369925.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/62787/original/czfcgdg3-1414369925.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/62787/original/czfcgdg3-1414369925.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/62787/original/czfcgdg3-1414369925.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/62787/original/czfcgdg3-1414369925.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/62787/original/czfcgdg3-1414369925.jpg?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">Topical insect repellents are the most effective way to prevent mosquito bites on exposed skin.</span>
<span class="attribution"><span class="source">Cameron Webb</span></span>
</figcaption>
</figure>
<h2>What is DEET?</h2>
<p>DEET was first synthesised through collaboration between the US Department of Defense and US Department of Agriculture in the late 1940s. The repellent became available to the public in 1957 and has since became the “gold standard” in topical insect repellents.</p>
<p>There is a <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1708-8305.2010.00402.x/full">considerable body of work</a> that demonstrates the effectiveness of DEET in providing protection from blood-seeking mosquitoes and DEET-based insect repellents are a mainstay of recommendations provided by <a href="http://www.health.nsw.gov.au/news/Pages/20140221_0.aspx">Australian health authorities</a> to reduce the risk of mosquito-borne disease.</p>
<p>If DEET is so effective, why the need to search for new repellents? The <a href="http://link.springer.com/article/10.1186/1756-3305-7-173">safety of DEET</a> continues to be raised but despite being used by millions of people every year, there are <a href="http://www.ajtmh.org/content/59/2/323.short">very few reported cases</a> of adverse health impacts if repellents are used as directed.</p>
<h2>We know it works … but how?</h2>
<p>We know from laboratory and field tests that DEET-based repellents stop mosquito bites, but there has been some debate surrounding the exact mode of action. Does DEET block the blood-feeding behaviour of mosquitoes or does it just smell so bad that mosquitoes actively avoid it?</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/62843/original/df4p2hst-1414383718.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/62843/original/df4p2hst-1414383718.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/62843/original/df4p2hst-1414383718.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=840&fit=crop&dpr=1 600w, https://images.theconversation.com/files/62843/original/df4p2hst-1414383718.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=840&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/62843/original/df4p2hst-1414383718.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=840&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/62843/original/df4p2hst-1414383718.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1056&fit=crop&dpr=1 754w, https://images.theconversation.com/files/62843/original/df4p2hst-1414383718.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1056&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/62843/original/df4p2hst-1414383718.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1056&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Well, it definitely works.</span>
<span class="attribution"><span class="source">PNAS</span>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>It has been described as a “<a href="http://www.nature.com/nature/journal/v478/n7370/abs/nature10438.html">confusant</a>” by some researchers who propose that it disrupts detection of host odours. Some conclude it can <a href="http://www.sciencemag.org/content/319/5871/1838.short">mask host odours</a>. Others have suggested mosquitoes <a href="http://www.pnas.org/content/105/36/13598.full">smell and actively avoid DEET</a>.</p>
<p>Once we understand how mosquitoes <a href="http://www.nature.com/nature/journal/v502/n7472/full/nature12594.html">detect and respond</a> to repellents, it will make the search for new mosquito repellent compounds more efficent. It may also help us understand the potential for mosquitoes to become <a href="http://www.pnas.org/content/107/19/8575.short">insensitive to DEET</a>.</p>
<p>In an attempt to settle the debate, researchers from the University of California, Davis studied the response of the southern house mosquito (<em>Culex quinquefasciatus</em>) to DEET, non-DEET insect repellents and a range of other chemical compounds. </p>
<p>By using a range of behavioural and electrophysiological approaches, the researchers showed that exposure to DEET activates an odour receptor, specifically CquiOR136, in the mosquito’s antennae.</p>
<p>Besides confirming that, at least in this mosquito species, an odorant receptor is critical in determining its repellency to DEET, it also provides an opportunity to screen for novel mosquito repellents.</p>
<p>Researchers looked to a new source of potential repellents, plants. Botanical extracts of plants, <a href="http://www.bioone.org/doi/abs/10.2987/09-0016.1">particularly essential oils</a>, have been extensively studied as possible insect repellents. </p>
<p>But what is interesting in this study is that the compound identified as a potential mosquito repellent, methyl jasmonate, is released by injured plants used to activate the <a href="http://www.pnas.org/content/87/19/7713.short">expression of defensive genes</a> in nearby plants. Could plant communications provide us with new mosquito repellents? </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/62791/original/4w9dr84g-1414371860.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/62791/original/4w9dr84g-1414371860.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/62791/original/4w9dr84g-1414371860.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/62791/original/4w9dr84g-1414371860.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/62791/original/4w9dr84g-1414371860.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/62791/original/4w9dr84g-1414371860.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/62791/original/4w9dr84g-1414371860.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/62791/original/4w9dr84g-1414371860.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">The southern house mosquito, <em>Culex quinequefasciatus</em>, was the subject of recent research to unravel the mystery of how DEET prevents mosquito bites. This mosquito is also common in many parts of Australia.</span>
<span class="attribution"><span class="source">C Webb</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<h2>Where to from here?</h2>
<p>While there have been many studies in recent times identifying <a href="http://www.abc.net.au/news/2013-10-03/researchers-shed-light-on-mystery-of-insect-repellent/4996848">new mosquito repellent candidates</a>, they rarely address one of the key issues that must be resolved: user compliance. </p>
<p>It could be argued that we don’t really need new topical mosquito repellents, but we need effective spatial repellents. Spatial repellents are new formulations that are passively released from devices and offer protection for a number of individuals – not just the person who has applied their topical repellent correctly.</p>
<p>Some synthetic insecticides, such as <a href="http://www.parasitesandvectors.com/content/6/1/262">metofluthrin</a>, already hold this potential. However, once we understand how mosquitoes detect and respond to new products we may be better able to develop new strategies.</p>
<p>These new repellents may be a while off yet so for this summer, stick to what is available and what we know works. Both DEET- and picaridin-based repellents will provide the longest lasting protection against mosquitoes. </p>
<p>Make sure you have a nice even coverage on all exposed areas of skin and reapply after a swim or sweaty activity. Stop the bites and you’ll reduce to risk of catching a mosquito-borne disease.</p><img src="https://counter.theconversation.com/content/33457/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Cameron Webb and the Department of Medical Entomology have been engaged by a range of insect repellent and insecticide manufacturers to provide testing of products and provide expert advice on mosquito biology.</span></em></p>The smell of mozzie repellent is as much a part of summer as barbecues and the cricket. Despite supermarket and pharmacy shelves overflowing with insect repellents, there are actually only a few active…Cameron Webb, Clinical Lecturer and Principal Hospital Scientist, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/109642013-01-03T18:50:35Z2013-01-03T18:50:35ZAussies vs mozzies: a user’s guide to repellents<figure><img src="https://images.theconversation.com/files/18906/original/96zyj2vy-1355887139.jpg?ixlib=rb-1.1.0&rect=0%2C18%2C640%2C411&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Not all mosquito repellents are equal.</span> <span class="attribution"><span class="source">Flickr/sachman75</span></span></figcaption></figure><p>Mosquito-borne disease is a serious concern, with millions of people worldwide impacted by pathogens spread by these blood-sucking insects. In Australia, there are more than <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1326-6756.2004.00436.x/full">5,000 cases of human illness</a> caused by the mosquito-borne Ross River virus and Barmah Forest virus every year. </p>
<p>When mosquitoes bite, they inject saliva into the skin. Our bodies react to this mozzie spit, causing a skin irritation. The severity of the “itchy bite” varies from person to person and, in some cases, <a href="http://www.sciencedirect.com/science/article/pii/S0091674904022183">severe allergic reactions can occur</a>.</p>
<p><a href="http://www.bioone.org/doi/abs/10.2987/10-6038.1">Mosquito control programs</a> can reduce the rates of human disease but the first line of defence remains personal protection measures: avoiding known mosquito habitats (such as wetlands) and peak biting times (dusk), wearing protective clothing (often treated with insecticides) and using bed nets and insect repellents. </p>
<p>But not all mosquito repellents are equal. There are over 60 individual repellent formulations currently registered including aerosols, creams, lotions, pump sprays, wipes, wrist bands and sticks. Despite this diversity of products, there are only a handful of active ingredients, the most common of which are DEET (diethyltoluamide) and Picaridin.</p>
<p>All topical insect repellents sold in Australia must be registered with the <a href="http://www.apvma.gov.au/">Australian Pesticides and Veterinary Medicines Authority</a> (APVMA). The APVMA assess products for their efficacy and safety. This also means the label must display the active ingredients and their concentration.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/18907/original/45vv5k5d-1355887461.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/18907/original/45vv5k5d-1355887461.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/18907/original/45vv5k5d-1355887461.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/18907/original/45vv5k5d-1355887461.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/18907/original/45vv5k5d-1355887461.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/18907/original/45vv5k5d-1355887461.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/18907/original/45vv5k5d-1355887461.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">Picaridin is often favoured because it’s as effective as DEET but doesn’t smell.</span>
<span class="attribution"><span class="source">Frlick/gfpeck</span></span>
</figcaption>
</figure>
<h2>Active ingredients</h2>
<p>DEET has been <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1708-8305.2010.00402.x/full">shown to be effective</a> at preventing bites from a wide range of pest mosquitoes. It’s considered the gold standard in mosquito repellents. But there is still not unanimous agreement on how DEET works. While it’s generally thought to prevent bites by inhibiting the host seeking stimuli, there is also some evidence that the <a href="http://www.pnas.org/content/105/36/13598.short">mosquitoes smell</a>, and are repelled, by DEET.</p>
<p>Picaridin works just as well as DEET and is generally considered to be a more pleasant product to use as it is odourless.</p>
<p>There is some resistance to the use of these chemical repellents because they’re unpleasant to use, are thought to damage clothing or belongings or are <a href="http://www.nejm.org/doi/full/10.1056/NEJMoa011699">perceived to pose adverse health effects</a>. But despite the widespread use of DEET, and increasingly picaridin, there are very few serious adverse reactions reported. As such, the two products have been endorsed by health authorities internationally as a <a href="http://www.sciencedirect.com/science/article/pii/S0273230008000494">safe way to avoid mosquito bites</a>.</p>
<h2>Formulations</h2>
<p>There is often confusion about how the concentration of a repellent determines the level of protection: the concentration of a repellent relates to the duration of protection, not the amount of mosquitoes that are kept at bay.</p>
<p>Repellents containing DEET at concentrations of 80% or 10%, for example, will both protect against mosquito bites for about two hours. While the protection provided by the 10% formulation may stop after a few hours, the 80% formulation will continue to provide protection for over ten hours.</p>
<p>When choosing a repellent, it’s worth keeping in mind just how long you’ll need to protect yourself. For a quick trip to the park, a low-concentration repellent will do the trick. But if you’re off on a major bush walk or fishing trip, a higher concentration repellent will be required. Alternatively, you’ll need to reapply a lower concentration repellent more frequently.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/18902/original/vjp4tbk8-1355886814.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/18902/original/vjp4tbk8-1355886814.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/18902/original/vjp4tbk8-1355886814.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/18902/original/vjp4tbk8-1355886814.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/18902/original/vjp4tbk8-1355886814.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/18902/original/vjp4tbk8-1355886814.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/18902/original/vjp4tbk8-1355886814.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 concentration of a repellent relates to the duration of protection, not the amount of mosquitoes that are kept at bay.</span>
<span class="attribution"><span class="source">Flickr/arnybo</span></span>
</figcaption>
</figure>
<p>So does formulation matter?</p>
<p>Probably not. The choice of active ingredient is really the most important decision. The choice of formulation is probably best guided by the ease of application. Sprays are generally most effective for arms and legs while creams and wipes are good for the face. </p>
<p>For complete protection, the entire surface of exposed skin must be covered. For this reason, it is probably best to apply repellent to your hands first, and then rub into exposed skin. A spray “here and there” won’t offer protection. Spraying repellent on clothes and/or belongings won’t help either.</p>
<h2>What about ‘natural’ repellents?</h2>
<p>Products derived from plants are often considered a safer alternative to the chemical products such as DEET and picaridin. Homemade concoctions of essential oils, particularly <em>Eucalyptus</em> and <em>Melaleuca</em> oils, are often promoted as suitable repellents.</p>
<p>First, it’s important to note that these products have the potential to <a href="http://www.jaad.org/article/S0190-9622%2894%2970050-8/abstract">cause skin reaction</a>. </p>
<p>Second, studies have shown that essential oils provide only <a href="http://www.bioone.org/doi/abs/10.2987/09-0016.1">limited protection</a> from biting mosquitoes. Registered commercial products that contain botanical extracts offer <a href="http://www.nejm.org/doi/full/10.1056/NEJMoa011699">some protection</a> but will need to be reapplied far more frequently than even the low concentration DEET- or picaridin-based repellents.</p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/18882/original/rvy228j7-1355881389.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/18882/original/rvy228j7-1355881389.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/18882/original/rvy228j7-1355881389.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/18882/original/rvy228j7-1355881389.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/18882/original/rvy228j7-1355881389.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/18882/original/rvy228j7-1355881389.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/18882/original/rvy228j7-1355881389.jpg?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">A spray ‘here and there’ won’t offer protection.</span>
<span class="attribution"><span class="source">Cameron Webb</span></span>
</figcaption>
</figure>
<p>Despite its popularity, citronella has repeatedly been shown to be <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1365-3156.2011.02781.x/full">less effective</a> than DEET.</p>
<p>The Australian native plant <em>Corymbia citriodora</em> (lemon-scented Gum) plant sits in an interesting position among botanical repellents. While the essential oil from this plant doesn’t demonstrate substantial repellent activity, the by-product of the hydrodistillation process has been shown to be a <a href="http://www.bioone.org/doi/abs/10.2987/8756-971X%282006%2922%5B507:PARBMR%5D2.0.CO%3B2">very effective repellent</a>. The active ingredient is p-menthane-3, 8-diol (<a href="http://www.apvma.gov.au/publications/gazette/2003/05/gazette0305p16.pdf">PMD</a>). In Australia, PMD is listed as, “Oil of Lemon Eucalyptus being acid modified extract of lemon eucalyptus (<em>Corymbia citriodora</em>)”. </p>
<p>Although patches or plastic wrist bands are registered as repellents by APVMA, these only offer very limited and localised protection (generally only immediately around the product, if at all).</p>
<p>Ultrasonic repellents have been sold in many forms for many years. The most recent incarnation is smartphone apps. The failure of sound to repel mosquitoes has been shown time and time again. <a href="http://www.bbc.co.uk/news/magazine-20669080">They simply don’t work</a>.</p>
<h2>What’s best?</h2>
<p>A <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1708-8305.2010.00402.x/full">group of experts</a> recently reviewed the benefits of a range of strategies, from insecticides to taking vitamin B supplements. </p>
<p>Their conclusion? As well as insecticide-treated bed nets and clothing, topical insect repellents provide the best protection. DEET- and picaridin-based repellents are a cheap, safe and effective way to prevent mosquito-borne disease. </p><img src="https://counter.theconversation.com/content/10964/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Cameron Webb and the Department of Medical Entomology have been engaged by a range of insect repellent and insecticide manufacturers to provide testing of products and provide expert advice on mosquito biology.</span></em></p>Mosquito-borne disease is a serious concern, with millions of people worldwide impacted by pathogens spread by these blood-sucking insects. In Australia, there are more than 5,000 cases of human illness…Cameron Webb, Clinical Lecturer and Hospital Scientist, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/84952012-07-27T04:29:19Z2012-07-27T04:29:19ZVIDEO: bed bugs at London 2012<figure><img src="https://images.theconversation.com/files/13519/original/hnhfwyvg-1343363116.jpg?ixlib=rb-1.1.0&rect=4%2C39%2C3014%2C2115&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Goodnight, sleep tight? Not if these critters have anything to do with it.</span> <span class="attribution"><span class="source">Lynn Friedman</span></span></figcaption></figure><p>In a co-production between <a href="http://www.sbs.com.au/news/">SBS World News Australia</a> and The Conversation, University of Sydney’s Cameron Webb explains why bed bugs will almost certainly bite at the London Olympics. It’s creepy. Enjoy.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/zAyyyRuQYxw?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>Read Cameron Webb’s full article: <a href="https://theconversation.com/will-bugs-bite-at-the-london-olympics-6616">Will bugs bite at the London Olympics?</a></p>
<p><strong>Further viewing:</strong></p>
<ul>
<li><a href="https://theconversation.com/video-why-is-australia-good-at-some-sports-and-not-others-8524">VIDEO: why is Australia good at some sports and not others?</a></li>
<li><a href="https://theconversation.com/video-what-is-the-economic-legacy-of-hosting-the-olympics-8572">VIDEO: what is the economic legacy of hosting the Olympics?</a></li>
<li><a href="https://theconversation.com/video-doping-drug-testing-and-the-olympics-8617">VIDEO: doping, drug testing and the Olympics</a></li>
<li><a href="https://theconversation.com/video-the-sports-legacy-of-the-olympic-games-8773">VIDEO: the sports legacy of the Olympic Games</a></li>
</ul><img src="https://counter.theconversation.com/content/8495/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Cameron Webb 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>In a co-production between SBS World News Australia and The Conversation, University of Sydney’s Cameron Webb explains why bed bugs will almost certainly bite at the London Olympics. It’s creepy. Enjoy…Cameron Webb, Clinical Lecturer and Hospital Scientist, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/63692012-04-19T04:19:51Z2012-04-19T04:19:51ZTaking the ouch and itch out of insect bites<figure><img src="https://images.theconversation.com/files/9674/original/4cnsz5y6-1334627529.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Biting insects cause allergic reactions because of their saliva, while stinging insects inject venom when they bite.</span> <span class="attribution"><span class="source">Emilio Floris/Wikimedia Commons</span></span></figcaption></figure><p>Mosquitoes, biting midges, bedbugs, ticks and fleas will make a meal of us given the opportunity. And it isn’t the pain or annoyance of the bite but our bodies’ reactions that often cause greater problems.</p>
<p>Biting insects are different to stinging insects. The former primarily cause allergic reactions due to the saliva they inject when feeding, while stinging insects (such as ants, bees and wasps) inject venom when they bite. </p>
<p>Insect venom causes pain and swelling at the site of the sting and may cause anaphylaxis. Reactions can be quite severe and include urticaria, nausea, vomiting, hypo-tension, respiratory problems and, in very rare cases, death. </p>
<p>The reddish, inflamed and swollen reactions to bites result from an injection of insect saliva. This is a chemical cocktail of substances designed to make blood flow quickly and painlessly to the bug as it tries to get its fill and avoid being squished.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/9669/original/smttfc6j-1334624867.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/9669/original/smttfc6j-1334624867.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=902&fit=crop&dpr=1 600w, https://images.theconversation.com/files/9669/original/smttfc6j-1334624867.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=902&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/9669/original/smttfc6j-1334624867.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=902&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/9669/original/smttfc6j-1334624867.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1134&fit=crop&dpr=1 754w, https://images.theconversation.com/files/9669/original/smttfc6j-1334624867.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1134&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/9669/original/smttfc6j-1334624867.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1134&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption"></span>
<span class="attribution"><span class="source">James West</span></span>
</figcaption>
</figure>
<p>As is the case with any environmental, food or chemical allergen, everyone has a different allergic response to insect saliva. That makes it pretty much impossible to identify the culprit from skin reaction alone. But it probably doesn’t really matter too much because treatment isn’t bug-specific.</p>
<h2>Scratch management</h2>
<p>A recent paper in <a href="http://dtb.bmj.com/lookup/doi/10.1136/dtb.2112.0099">Drug and Therapeutics Bulletin</a> looks into how we commonly manage insect bites. It highlighted the scarcity of quantitative scientific studies into the various treatments for insect bite reactions. </p>
<p>The authors found that the few published papers reported little evidence that currently recommended over-the-counter remedies in the United Kingdom for simple insect bites actually work. But they acknowledge that such medications may offer some relief for the discomfort associated with insect bites. </p>
<p>A <a href="http://www.racgp.org.au/afp/200911/200911beach.pdf">recent Australian study</a> also found insect bites were commonly managed with similar over-the-counter medications.</p>
<h2>But does it work?</h2>
<p>First and foremost, it’s important to avoid insect bites. Notwithstanding nuisance biting, the transmission of disease-causing pathogens associated with insect bites is a major cause for concern in some areas of Australia. </p>
<p>There’s a <a href="http://medent.usyd.edu.au/arbovirus/mosquit/repellent_guidelines_2011.pdf">range of strategies</a> that can be used indoors and outside to beat biting insects. They include using insecticides, topical insect repellents and physical barriers such as fly screens and bed nets. But what happens if a pesky insect slips past our defences?</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/9506/original/6xgjzgns-1334194112.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/9506/original/6xgjzgns-1334194112.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/9506/original/6xgjzgns-1334194112.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/9506/original/6xgjzgns-1334194112.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/9506/original/6xgjzgns-1334194112.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/9506/original/6xgjzgns-1334194112.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/9506/original/6xgjzgns-1334194112.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 common brown house mosquito, <em>Culex quinquefasciatus</em>, is responsible for many of the bites we receive while asleep at night.</span>
<span class="attribution"><span class="source">Stephen Doggett, Medical Entomology, Westmead Hospital</span></span>
</figcaption>
</figure>
<p>A mild reaction to an insect bite will probably resolve itself within a day or two without any need for treatment. And if there’s discomfort caused by swelling or itchiness, a cold compress can often provide sufficient relief. But, in some cases, the use of a topical steroid may assist in reducing inflammation and an antipruritic may relieve itchiness. </p>
<p>Oral analgesics or antihistamines may provide relief for serious reactions but it’s probably best to discuss the most suitable products with your doctor or pharmacist. Antibiotics are rarely required for insect bites alone – generally only if a secondary infection occurs.</p>
<h2>Bite-ridden children</h2>
<p>Reactions to insect bites can often be worse in young children. Their little bodies haven’t had a chance to build up immunity so they’re more likely to react more noticeably than older children and adults. This adds an extra level of anxiety in their carers. </p>
<p>But the worst result of most insect bites is largely self-inflicted from scratching. Intense itchiness leading to incessant scratching will likely result in broken skin and secondary bacterial infection. This can become difficult to deal with but despite many reactions among children appearing quite dramatic, serious outcomes from insects bites are relatively rare. </p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/9645/original/4mks9ny9-1334553143.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/9645/original/4mks9ny9-1334553143.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/9645/original/4mks9ny9-1334553143.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/9645/original/4mks9ny9-1334553143.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/9645/original/4mks9ny9-1334553143.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/9645/original/4mks9ny9-1334553143.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/9645/original/4mks9ny9-1334553143.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Children are often have more severe reactions due to a less built up immune system.</span>
<span class="attribution"><span class="source">maryfrancesmain/ Flickr</span></span>
</figcaption>
</figure>
<p>The most important thing is to ensure that the bite site is kept clean and dry, and scratching is kept to a minimum. As soon as the skin is broken, there’s a chance of secondary infection that may result in a more significant reaction requiring antibiotics. </p>
<p>Most children’s reactions to insect bites will naturally become less dramatic as they get older.</p>
<h2>Home remedies</h2>
<p>There’s a whole host of home remedies purported as effective treatment for insect bites. These range from essential oils to mixtures of bicarbonate soda, but there’s no scientific evidence that they’ll provide relief. Most importantly, many home-made concoctions run the risk of causing a skin reaction themselves.</p>
<p>With insect bite skin reactions varying so greatly between people, it’ll always be difficult to have a “one-size-fit-all” approach to their treatment. Some medications may provide relief from severe allergic reaction. but for the majority of cases, that annoying, itchy little bite will just have to resolve on its own.</p><img src="https://counter.theconversation.com/content/6369/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>In his position with Medical Entomology, University of Sydney and Westmead Hospital, Cameron provides advice to local, state and federal authorities on arthropods of public health concern. Medical Entomology also receives funding from the private sector for evaluation of insecticides, repellents and other personal protection technologies.</span></em></p>Mosquitoes, biting midges, bedbugs, ticks and fleas will make a meal of us given the opportunity. And it isn’t the pain or annoyance of the bite but our bodies’ reactions that often cause greater problems…Cameron Webb, Clinical Lecturer and Hospital Scientist, University of SydneyLicensed as Creative Commons – attribution, no derivatives.