tag:theconversation.com,2011:/ca/topics/sadc-malaria-week-22253/articlesSADC malaria week – The Conversation2018-11-07T13:10:46Ztag:theconversation.com,2011:article/1063682018-11-07T13:10:46Z2018-11-07T13:10:46ZSouth Africa investigates sterilising mosquitoes in anti-malaria drive<figure><img src="https://images.theconversation.com/files/244111/original/file-20181106-74787-1d6j2in.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A close-up of a female Anopheles arabiensis feeding. </span> <span class="attribution"><span class="source">Author supplied</span></span></figcaption></figure><p>South Africa is one of four southern African countries aiming to <a href="https://medpharm.tandfonline.com/toc/ojid20/current">eliminate malaria transmission</a> by 2023. Indoor residual spraying using DDT and pyrethroid insecticides constitutes the backbone of South Africa’s <a href="http://www.samj.org.za/index.php/samj/article/view/7447/5462">malaria control programmes</a>. </p>
<p>Effective vector control by indoor residual spraying has been key in the reduction of malaria cases. This was instrumental in creating malaria-free zones in most parts of the country. Malaria transmission is now <a href="http://www.samj.org.za/index.php/samj/article/view/7441/5461">limited</a> to the north-eastern parts of Limpopo province, the low-veld areas of Mpumalanga province and the far northern parts of KwaZulu-Natal province. </p>
<p>Despite a concerted effort to eliminate malaria in these provinces, transmission has remained steady over the <a href="http://www.samj.org.za/index.php/samj/article/view/7441/5461">past decade</a>.</p>
<p>Failure to eliminate malaria transmission is attributed, in part, to resistance to the insecticides being used. Added to this is the challenge of controlling the outdoor-biting <em>Anopheles arabiensis</em> population that’s largely considered responsible for most malaria transmission in the country. </p>
<p>Indoor spraying isn’t completely effective against this mosquito because it mainly targets indoor biting and resting mosquitoes. This strategy is not adequate against vectors that sometimes feed and rest outdoors, such as <em>An. arabiensis</em>. </p>
<p>Other, complementary vector control strategies are needed to eliminate the disease. These must be able to control outdoor feeding and resting mosquito populations. </p>
<p>One possible approach is a technique that involves sterilising the insects. The technology is currently being assessed in South Africa. The technique involves a genetic birth control method in which laboratory mass-produced sterile male insects are released into the wild at a ratio that effectively inundates a target population. This forces most females to mate with sterile males, substantially reducing their fecundity, and resulting in population suppression. </p>
<p>The sterile insect technique has been piloted against <a href="https://www.springer.com/us/book/9781402060588">mosquito vectors</a> of the Zika, yellow fever, chikungunya and dengue viruses, but has never been used for malaria control efforts. The South African sterile insect technique initiative together with a similar trial in <a href="https://link.springer.com/chapter/10.1007/978-1-4020-6059-5_34">Sudan</a> are a first for African malaria vectors. </p>
<p>Preparations for the South African project are at an advanced stage. A pilot mass-rearing facility has been built and the size of the natural mosquito population has been estimated. In addition, a local community has been drawn into preparations and is now ready for a trial run. All these steps pave the way for a pilot demonstration.</p>
<h2>The project</h2>
<p>The sterile insect technique has been applied successfully against <a href="http://agris.fao.org/agris-search/search.do?recordID=US9032290">other insect pests</a> including the fruit fly and the new-world screwworm fly . In South Africa this technology is routinely used in Citrusdal, Western Cape to control the <a href="http://www.bioone.org/doi/abs/10.4001/003.023.0112">false codling moth</a>.</p>
<p>The <a href="http://www.parasitesandvectors.com/content/4/1/208">project</a> involving <em>An. arabiensis</em> aims to show that the sterile insect technique can be successfully used to suppress mosquito populations that carry and spread malaria. If it works, the approach can be used as an alternative vector control method to complement existing strategies. </p>
<p>The project is being implemented in three phases. </p>
<p>Phase 1 included trials showed that sterilised <em>An. arabiensis</em> males mass-reared under laboratory conditions can compete with fertile males for mates. This milestone informed phase II of the project which is currently underway.</p>
<p>This phase aims to test the feasibility of the sterile insect technique through a small-scale pilot field demonstration in northern KwaZulu-Natal. Research activities for phase II are in progress. The biggest development here is the building of Africa’s first pilot mosquito mass-rearing facility.</p>
<p>The sterile insect technique relies heavily on inundating the wild population with sterilised male insects. For this to succeed, it’s important to know the size of the wild mosquito population as this will determine how many laboratory-reared sterilised males would need to be released. </p>
<p>To estimate mosquito population numbers, a mark-release-recapture method was used. About 30,000 yellow and orange-dusted laboratory-reared males sharing the same genetic background as the wild population were released over two release periods. Some of these mosquitoes were recaptured together with wild mosquitoes and a formula was used to estimate the wild population size. </p>
<p>Interestingly, marked males were recaptured in swarms of wild males. This indicates that the laboratory-reared males were able to locate and participate in mating swarms – a crucial step for the potential success of the sterile insect technique.</p>
<h2>Next steps</h2>
<p>The eventual rollout of the pilot trial will require successful mass rearing of competitive sterile males and a technique to separate males from female insects. Work on optimising mass production of quality sterile male and a system to separate males from females are at an advanced stage. </p>
<p>In addition, it’s critical to get the community involved and addressing any social issues so that people cooperate and participate. This is particularly important because the sterile insect technique can be seen as increasing the numbers of mosquitoes in an area after the release of the sterile males. A malaria awareness campaign has already been conducted. Information on malaria transmission and control – including the potential of using the sterile insect technique – was shared through radio interviews, brochures, road shows and lectures in isiZulu.</p><img src="https://counter.theconversation.com/content/106368/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Givemore Munhenga receives funding from Department of Science and Technology, National Research Foundation and International Atomic Energy Agency. He is affiliated with University of the Witwatersrand. </span></em></p>South Africa is piloting a new technique as it drives to eliminate malaria.Givemore Munhenga, Senior Medical Scientist, National Institute for Communicable DiseasesLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/498732015-11-04T04:05:01Z2015-11-04T04:05:01ZSeven things worth knowing about mosquitoes<figure><img src="https://images.theconversation.com/files/100535/original/image-20151102-16527-1dthulh.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Anopheles Gambiae, one of three mosquitoes found in Africa that transmit malaria.</span> <span class="attribution"><span class="source">shutterstock</span></span></figcaption></figure><p><em><em>This article is part of a series The Conversation Africa is running as part of the South African Development Community malaria week. You can read the rest of the series <a href="https://theconversation.com/africa/topics/sadc-malaria-week">here</a>.</em></em></p>
<p><strong>1. Not all mosquitoes bite.</strong></p>
<p>The female mosquitoes are the dangerous ones. They bite and draw blood. Male mosquitoes feed on flower nectar. Males have very hairy and fuzzy antennae (like a powder puff) whereas females have less hairy antennae. </p>
<p><strong>2. There are three types of malaria carrying mosquitoes.</strong></p>
<p>The top three malaria transmitters in Africa are Anopheles gambiae, Anopheles funestus and Anopheles arabiensis. The first two live in areas of Africa where there is higher rainfall while the third, Anopheles arabiensis, is a more savanna-based, arid zone species. </p>
<p>Gambiae and funestus prefer to feed indoors and are strongly attracted to humans, but arabiensis feeds as easily outdoors as indoors and also as easily on cattle and other animals as humans. This means it is easier to target gambiae and funestus using indoor methods such as spraying walls with insecticides and using insecticide-impregnated bed nets. The outdoor-feeding arabiensis is far more difficult to control. </p>
<p>In most areas all three species have a peak of biting in the early hours of the morning when people are in their deepest sleep and less likely to disturb mosquitoes during the feeding process. There are also other important species of malaria-transmitting mosquitoes but they are more localised in distribution.</p>
<p><strong>3. Mosquitoes have started to change their feeding patterns.</strong></p>
<p>Because of the strong focus on indoor strategies to fight malaria transmitting mosquitoes using bed nets and indoor spraying, genetic selection is resulting in some populations of these mosquitoes biting outdoors and earlier at night when people are not protected by bed nets. It means these mosquitoes are more difficult to reach with insecticides, just as is the case with Anopheles arabiensis.</p>
<p><strong>4. Most mosquito bites are harmless. It’s only the ones that carry certain types of parasites that lead to malaria, and potentially death.</strong></p>
<p>In Africa, there are four known species of microscopically small parasites that can cause the disease we call malaria. All four belong to the group <em>Plasmodium</em>. The most common of these parasites in Africa is <em>Plasmodium falciparum</em>, which is the most deadly of the four species. </p>
<p>Birds and some other groups of animals carry their own species of <em>Plasmodium</em>, which is also transmitted by mosquitoes, but they do not cause malaria in humans. Mosquitoes also carry many other disease-causing organisms such as yellow fever virus, West Nile virus, Rift Valley fever, and the worms that cause the dreaded disfiguring elephantiasis (filariasis).</p>
<p><strong>5. Mosquitoes select where they feed on the body. They have very acute sensory mechanisms (like heat-seeking missiles) that lead them to select particular parts of the body (such as ankles) to feed from.</strong></p>
<p>All three of the main malaria carrying mosquitoes have similar biting preferences. If you are sitting or standing outside in the evening the overwhelming majority will try to feed on your ankles and feet - so make sure you cover these areas with repellent or wear socks and shoes.</p>
<p>The antennae of mosquitoes are highly specialised sensory organs that can detect very small amounts of chemical cues that lead them to food and mates. Various chemicals, of which carbon dioxide is one, help female mosquitoes track down their hosts. Pheromones, which are hormones secreted as odours into the environment, enable males and females to meet and mate. They are also detected by the antennae.</p>
<p><strong>6. Malaria mosquitoes do not like wind.</strong></p>
<p>Using a fan over you when going to bed will lessen your chances of being bitten. These mosquitoes don’t like flying when there is even a slight breeze.</p>
<p><strong>7. 97 countries and territories still face ongoing malaria transmission.</strong></p>
<p>According to the World Health Organisation, an estimated 3.2 billion people, or just under half the world’s population, are at risk of getting malaria. The bulk of the malaria burden is shouldered by Africa where 89% of cases and 91% of deaths occur.</p><img src="https://counter.theconversation.com/content/49873/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Professor Leo Braack received funding from Bill & Melinda Gates Foundation and also University of Pretoria to conduct malaria research</span></em></p>The irritating buzz that rings in your ear in the dead of the night comes from an insect barely traceable with your naked eye. Here are a few facts worth knowing about the mosquito.Leo Braack, Research Chair, Integrated Vector Management in the Vector Control Cluster, Centre for Sustainable Malaria Control , University of PretoriaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/499862015-11-03T04:06:11Z2015-11-03T04:06:11ZThe quest to find a drug that nails the tricky malaria parasite<figure><img src="https://images.theconversation.com/files/100525/original/image-20151102-16554-rjrqi5.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A doctor observes mosquitoes to better understand the malaria parasite which has been developing a resistance to the anti-malarial drugs.</span> <span class="attribution"><span class="source">Reuters/RIcardo Rojas</span></span></figcaption></figure><p><em><em>This article is part of a series The Conversation Africa is running during malaria week in the Southern African Development Community. You can read the rest of the series <a href="https://theconversation.com/africa/topics/sadc-malaria-week">here</a>.</em></em></p>
<p>Malaria is a killer that has spent thousands of years adapting to the habits of its victim. Although the first confirmed case of human malaria dates to 450 AD, a millennia and a half later, the world is still battling the parasite that causes this disease. Today at least <a href="http://www.who.int/malaria/media/world_malaria_report_2014/en/">3.3 billion</a> people, or almost half of the world’s population, are at risk of contracting malaria. The heaviest burden is in Africa where an estimated 90% of malaria deaths occur.</p>
<p>To eliminate malaria and alleviate the disease scientists have to develop drugs that kill the parasite in the blood. But to prevent the spread of the disease in a community, these drugs also have to kill transmissible versions of the parasite that develop. </p>
<p>The challenge is that the world is running out of usable antimalarial <a href="http://www.who.int/malaria/media/world_malaria_report_2014/en/">drugs</a>. Antimalarial drugs that are widely used have a limited usable lifespan. This is because parasites develop resistance. The current drugs are becoming less effective as the parasite develops resistance against them. </p>
<p>To tackle this problem, researchers are investigating potential antimalarial drugs with multiple <a href="http://www.biomedcentral.com/content/pdf/s12936-015-0572-z.pdf">targets</a> to overwhelm the parasite and reduce resistance development. Multi-target drugs may also speed up the drug discovery and development process.</p>
<p>The multi-target inhibitors that we are <a href="http://www.biomedcentral.com/content/pdf/s12936-015-0572-z.pdf">studying</a> have been shown to target both the disease causing and transmissible forms.</p>
<h2>Understanding the malaria parasite</h2>
<p>The malaria parasite is an amazing shape shifter. It is able to change its shape in different environments to cause and spread the disease. In infected humans, the parasite lives within red blood cells leading to the symptoms and complications of the disease. The main symptoms include fever, headaches and vomiting which usually appear between 10 and 15 days after the mosquito <a href="http://www.who.int/topics/malaria/en/">bite</a>.</p>
<p>But when a female mosquito bites a human infected with malaria, a special form of the parasite, called a gametocyte, is drawn up from the person along with their blood. This special parasite then develops further in the newly infected mosquito and matures into another form of parasite that can be transferred to another human when the mosquito bites someone else. This leads to the spread of malaria. </p>
<p>With repeated exposure to a drug, the parasite cleverly adapts to the presence of the drug by changing its DNA. This means that the drug target in the parasite is no longer affected by the drug or that the parasite gets rid of the drug before it can reach its target. </p>
<p>To slow down the ability of the parasite to develop drug resistance, malaria medicine has been formulated into a combination therapy. It combines two antimalarial drugs that target different biological processes in a single tablet. It is considerably more difficult for the parasite to simultaneously change both targets in order to become resistant against both drugs. With combination therapies, the parasite has a significantly reduced chance of developing resistance compared to a single therapy. </p>
<p>Even though combination therapies have assisted in slowing down parasite drug resistance, the parasite is developing drug resistance to an antimalarial drug faster than new drugs are being developed and approved. </p>
<h2>A multi-pronged approach</h2>
<p>To increase and sustain the antimalarial armoury, drug developers need to deliver drugs faster and increase the lifespan of the drugs that are in circulation. </p>
<p>The answer to this conundrum may lie in the field of antibiotic drug discovery. </p>
<p>The antibiotic field is currently developing resistance-resistant <a href="http://www.cell.com/trends/pharmacological-sciences/abstract/S0165-6147(14)00172-2">antibiotics</a> that have multiple targets instead of single targets. Instead of a combination therapy that targets two single targets, a multi-target drug has numerous targets which the parasites need to develop resistance against. This makes it exponentially more effective than a combination therapy in resisting resistance. </p>
<p>One example of the outstanding success of this strategy is the TB drug, <a href="http://openres.ersjournals.com/content/1/1/00010-2015.full">SQ109</a>, which is currently in phase II clinical trials. It inhibits multiple targets with potent inhibition of TB cell growth and very low rates of spontaneous drug resistance. </p>
<p>A multi-target drug approach may provide the desired drug discovery breakthrough required to treat malaria. It would speed up the delivery of candidates into clinical practice and decrease drug resistance. </p>
<p>Ultimately, it would stop the spread of malaria by targeting the transmissible forms. In this way, we hope to stay one step ahead of the malaria parasite and make a dramatic difference to curb and eliminate the disease.</p><img src="https://counter.theconversation.com/content/49986/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Bianca Verlinden receives funding from the SA National Research Foundation and SA Medical Research Council. </span></em></p><p class="fine-print"><em><span>Lyn-Marie Birkholtz receives research funding from the SA National Research Foundation and the SA Medical Research Council. </span></em></p>Across the world scientists are trying to find a new drug that the malaria carrying parasite will struggle to develop a resistance to.Bianca Verlinden, Postdoctoral Research Fellow, Molecular Parasitology, Department of Biochemistry, University of PretoriaLyn-Marie Birkholtz, Associate Professor (Biochemistry) DST/NRF South African Research Chair (SARChI) in Sustainable Malaria Control, University of PretoriaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/498482015-11-01T11:07:52Z2015-11-01T11:07:52ZParts of southern Africa are within tantalising reach of eliminating malaria<figure><img src="https://images.theconversation.com/files/100338/original/image-20151030-16554-1qj7h1i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A young girl plays inside a mosquito net in Kibera, Nairobi. </span> <span class="attribution"><span class="source">EPA/Stephen Morrison</span></span></figcaption></figure><p><em><em>This article is part of a series The Conversation Africa is running as part of the SADC malaria week. You can read the rest of the series <a href="https://theconversation.com/africa/topics/sadc-malaria-week">here</a>.</em></em></p>
<p>There has been a concerted international effort since the early 2000s to tackle malaria. This has led to dramatic reductions in the disease. </p>
<p>World Health Organisation estimates show that in 2015 there were <a href="http://www.who.int/malaria/media/malaria-mdg-target/en/">214 million</a> malaria cases and 438,000 deaths globally. This is a 37% decrease in the incidence rate of malaria compared to 15 years ago and a 60% reduction in deaths.</p>
<p>Most of the gains have happened in Asia and “fringe” areas in Africa, which is at the periphery of distribution of the disease. But the challenge is that sub-Saharan Africa still shoulders 89% of existing cases and 91% of deaths from the disease. </p>
<h2>How successes have been achieved</h2>
<p>Africa has historically had a high transmission rate. Southern Africa has been particularly successful in reducing its case load. The Seychelles and Mauritius have completely eliminated malaria. They have had no new local transmissions in recent years – only some imported cases that were locally diagnosed and treated.</p>
<p>In South Africa there was an exceptional peak of <a href="http://www.scielo.org.za/scielo.php?pid=S0256-95742013001000029&script=sci_arttext&tlng=es">64,622 cases</a> in 2000. Since then case numbers have dwindled to between 6000 and 10,000 in recent years. </p>
<p>This reflects reductions in several of South Africa’s neighbouring countries such as Botswana, Namibia, and Swaziland – where malaria mortality rates are close to zero. </p>
<p>These four countries are in the pre-elimination and elimination stages. Malaria incidence in all of them makes up less than five cases per thousand people. This means they are within sight of eliminating malaria – a tantalising target that South Africa hopes to reach <a href="http://www.scielo.org.za/scielo.php?pid=S0256-95742013001000035&script=sci_arttext&tlng=en">by 2018</a>.</p>
<p>But that reward is proving hard to achieve despite the dedicated efforts by the national malaria control programs in each country. </p>
<h2>The reasons why full elimination is so difficult</h2>
<p>The standard tools used almost universally for malaria control are: </p>
<ul>
<li><p>providing households with insecticide-treated bednets (ITNs);</p></li>
<li><p>indoor residual spraying (IRS) of insecticides against mosquitoes that enter households; and</p></li>
<li><p>dedicated efforts to detect malaria cases and treat them with effective anti-malarial drugs. </p></li>
</ul>
<p>When these three tools are used in combination, they have resulted in the reversal and decline in malaria cases almost globally. But what was once an effective approach to harvest the low-hanging fruit to achieve relatively quick success have now become blunt tools. </p>
<p>The interventions now lack the surgical precision to clear up what is known as “residual malaria”. These are the portion of cases that pop up for reasons that are not always known and do not yield to persistent use of the traditional tools.</p>
<p>A major contributing factor, especially in the case of South Africa, is the large numbers of migrants and visitors from high-transmission malaria countries further north. Although Gauteng, South Africa’s economic hub, was never a problem province, it now has the highest number of cases in the country.</p>
<p>The cases are through infected people entering the country and becoming ill once they have arrived, or vehicles returning from high-transmission countries with malaria-infected mosquitoes hitching a ride.</p>
<p>There are other reasons too. </p>
<p>Some countries do not have a policies to deal effectively with the particular life stages that infect mosquitoes. Malaria parasites have a complex life cycle involving different forms having different target organs and functions. Only one stage – the sexual gametocytes – are able to infect mosquitoes that leads to infecting other people. </p>
<p>Although doctors prescribe medication that kills the numerous asexual parasites in the blood which then cures infected people of the malaria symptoms, it does not effectively inactivate the sexual gametocytes that infect mosquitoes, at least in Africa where the deadliest species of malaria parasite is most common.</p>
<p>There are also chronic systemic challenges. These include a shortage of manpower, funding, lost skills that are not replaced, and a mindset still geared to the decades-long traditional approach to combat malaria. </p>
<h2>New frontier</h2>
<p>Entering the elimination stage is a relatively new frontier for the southern African countries. </p>
<p>There are more hazy possibilities that come into play with residual malaria. This includes the unknown role of secondary vectors. Traditional malaria control tools have targeted a very limited set of mainly <a href="http://www.parasitesandvectors.com/content/3/1/72">three mosquito species</a> with known behaviour. </p>
<p>Addressing these three species has resulted in successes. But with residual malaria we may be dealing with unknown secondary vector mosquitoes that previously played a minor role but now keep the disease ticking over.</p>
<p>Also, across the world there are increasing numbers of countries where mosquito populations are building resistance to available insecticides used for spraying. What is more concerning is that malaria parasites are also developing resistance to the only, and best, available anti-malarial compound, artemisinin.</p>
<p>This resistance is currently still confined to geographic pockets in southeast Asia, but precedents exist where such resistance rapidly spreads to other parts of the globe.</p>
<p>Another concern is loss of political will to continue the high financial and other demands associated with effective malaria programs – and donor fatigue. </p>
<p>Most of the money being poured into malaria control at global scale comes from international donors. Once again precedent has shown that in the face of diminishing returns such donors lose commitment.</p>
<h2>The last lap</h2>
<p>Botswana, Namibia, South Africa and Swaziland – unlike many other African countries confronted with particular economic and political challenges – are very likely to achieve zero local transmission. </p>
<p>The lessons learnt in South Africa and its neighbours is of great importance. There is some urgency in cementing these successes. </p>
<p>But then the real challenge will emerge: the will of national governments to continue funding a program that has achieved its goal. The moment it weakens its defences, malaria is likely to rebound extremely quickly in the face of migration and importation from high-transmission neighbouring countries that are still fighting to bring malaria under control.</p><img src="https://counter.theconversation.com/content/49848/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Professor Leo Braack received funding from Bill and Melinda Gates Foundation and University of Pretoria for research on malaria.</span></em></p>Several countries within southern Africa are on the brink of eliminating malaria. But there are several challenges ahead.Leo Braack, Research Chair, Integrated Vector Management in the Vector Control cluster at the Centre for Sustainable Malaria Control , University of PretoriaLicensed as Creative Commons – attribution, no derivatives.