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It’s warming up and mozzies are coming. Here’s how to mosquito-proof your backyard

<p><em><a href="https://theconversation.com/profiles/cameron-webb-6736">Cameron Webb</a>, <a href="https://theconversation.com/institutions/university-of-sydney-841">University of Sydney</a></em></p> <p>The weather is warming up and that means more time in the backyard. It also means more mosquitoes.</p> <p>Here are five ways you can mosquito-proof your backyard that <a href="https://theconversation.com/the-battle-against-bugs-its-time-to-end-chemical-warfare-111629">don’t rely on spraying insecticides</a>.</p> <h2>1. Get rid of water</h2> <p>Mosquitoes need water to complete their life cycles. They <a href="https://theconversation.com/feel-like-youre-a-mozzie-magnet-its-true-mosquitoes-prefer-to-bite-some-people-over-others-128788">need blood</a> – but water and warmth are just as important.</p> <p>Getting rid of water around your backyard will go a long way to keeping mosquitoes away. Water trapped in blocked roof gutters, drains and tarpaulin covering boats and trailers can be a great home for mosquitoes.</p> <p>Mosquitoes can exploit the tiniest of water sources too. It may just be the upturned lid of a discarded plastic drink bottle. If it traps water, mosquitoes will find it and lay eggs in it.</p> <p>Flush out your bird bath once a week to disrupt the mosquito’s life cycle.</p> <p>If you have a pond, installing a fountain will discourage mosquitoes. If you can’t keep water clean and circulating, consider filling it with sand and gravel to create an interesting garden bed for succulents or other plants.</p> <p>Mosquitoes will avoid clean and chlorinated swimming pools but will quickly move into “green pools”. If you’re not using your pool, consider <a href="https://www.krg.nsw.gov.au/Environment/Your-local-environment/Wildlife/Living-with-wildlife/Pool-to-pond/How-to-convert-your-pool">converting it to a “pond”</a> so that fish can help keep mosquito numbers down.</p> <h2>2. Screen up – windows, doors and rainwater tanks</h2> <p>If you can’t get rid of permanent water, at least stop mosquitoes getting to it (or you).</p> <p>Ensure <a href="https://www.brisbane.qld.gov.au/clean-and-green/natural-environment-and-water/water/water-smart-homes/rainwater-tanks/using-your-rainwater-tank">rainwater and septic tanks</a> have screens to stop mosquitoes entering.</p> <p>Screen windows and doors to stop mosquitoes entering the home. There are plenty of flexible screening options for windows, doors and balconies.</p> <p>If you live in a mosquito-prone area, creating a screened outdoor area (such as a pergola, courtyard, or balcony) will give you the opportunity to spend time outdoors without being hassled by mozzies.</p> <h2>3. Choose your garden plants carefully</h2> <p>Some plants <a href="https://bioone.org/journals/Journal-of-the-American-Mosquito-Control-Association/volume-25/issue-3/09-0016.1/Are-Commercially-Available-Essential-Oils-from-Australian-Native-Plants-Repellent/10.2987/09-0016.1.short">contain essential oils and other chemicals</a> that, when extracted and concentrated, provide protection against biting mosquitoes. But there isn’t a lot of evidence that the whole plant will keep mosquitoes away from your garden.</p> <p>Some types of plants are even marketed as “mozzie blockers” or “mosquito repelling”. But there isn’t <a href="https://www.veranda.com/outdoor-garden/a40592197/do-mosquito-repelling-plants-work/">any evidence of effectiveness</a>. In fact, some of these plants, <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/j.1440-6055.2009.00736.x">such as melaleucas</a>, also happen to be associated with <a href="https://academic.oup.com/jme/article/36/4/515/903838">hot spots of mosquito breeding</a> in coastal Australia.</p> <p>The plants to <em>avoid</em> around the home are those that help mosquitoes breed, such as <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1440-6055.2008.00641.x">bromeliads</a>, which trap water.</p> <h2>4. Encourage the animals that eat mosquitoes</h2> <p>Mosquitoes are food for a range of animals including birds, bats, fish, frogs, lizards, insects, spiders and <a href="https://besjournals.onlinelibrary.wiley.com/doi/abs/10.1111/1365-2656.13965">dragonflies</a>. But don’t expect them to eat enough to keep all mosquitoes away.</p> <p>Bats are often promoted as a good “biological control” options but studies have shown mosquitoes are <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0077183">more likely to be a snack food</a> for small bats, not an irresistible staple of their diet.</p> <p>For garden ponds, frogs will eat a few adult mosquitoes but tadpoles of Australian frogs generally <a href="https://bioone.org/journals/journal-of-the-american-mosquito-control-association/volume-21/issue-4/8756-971X(2006)21%5b492%3aTOFCAF%5d2.0.CO%3b2/TADPOLES-OF-FOUR-COMMON-AUSTRALIAN-FROGS-ARE-NOT-EFFECTIVE-PREDATORS/10.2987/8756-971X(2006)21%5B492:TOFCAF%5D2.0.CO;2.short">don’t eat many mosquito “wrigglers”</a>.</p> <p>Australian native fish <a href="https://pubmed.ncbi.nlm.nih.gov/15532929/">will readily eat mosquitoes</a> and may be useful for backyard ponds.</p> <p>But not all fish are good. While “mosquitofish” (aka “plague minnow”) is distributed overseas to assist in mosquito control, <a href="https://meridian.allenpress.com/australian-zoologist/article/30/3/316/134508/Does-predation-by-the-fish-Gambusia-holbrooki">it’s a disaster for local wildlife</a> and, <a href="https://www.dpi.nsw.gov.au/fishing/aquatic-biosecurity/pests-diseases/freshwater-pests/finfish-species/gambusia">along with other exotic fish species</a>, should not be released into local waterways.</p> <p><a href="https://link.springer.com/article/10.1007/s13157-019-01133-2">Healthier habitats promote fewer mosquitoes</a> so the best thing you can do is create habitats for the animals that eat mosquitoes.</p> <h2>5. Avoid traps and other gadgets</h2> <p>There are lots of devices purported to catch, kill, or repel mosquitoes from your garden. Some may catch a mosquito or two but they’re not very effective in knocking out big numbers.</p> <p>“Bug zappers” with bright lights will collect lots of flying insects. It’s just that mosquitoes make up a very small proportion of collections.</p> <p>Electrocuting devices, again, don’t seem to attract a lot of mosquitoes.</p> <p>Devices that <a href="https://theconversation.com/the-buzz-from-your-smartphone-wont-stop-mosquito-bites-92611">emit high frequency sounds</a> won’t help either.</p> <p>The best devices are typically those that are baited with carbon dioxide. These are a mainstay of state and territory <a href="https://www.health.nsw.gov.au/Infectious/mosquito-borne/Pages/surveillance.aspx">mosquito and arbovirus surveillance programs</a>. For a mosquito, the C0₂ tricks them into thinking the trap is a warm-blooded animal. The only problem is these can be expensive to run and don’t seem quite as effective for mosquito control <a href="https://bioone.org/journals/journal-of-the-american-mosquito-control-association/volume-22/issue-3/8756-971X(2006)22%5b490%3aTATTFA%5d2.0.CO%3b2/Traps-and-Trapping-Techniques-for-Adult-Mosquito-Control/10.2987/8756-971X(2006)22%5B490:TATTFA%5D2.0.CO;2.short">unless used in large numbers</a>.</p> <h2>Yes, you’ll still need repellent</h2> <p>Perhaps the best way to avoid mosquito bites is to pick an insect repellent <a href="https://www.phrp.com.au/issues/december-2016-volume-26-issue-5/a-review-of-recommendations-on-the-safe-and-effective-use-of-topical-mosquito-repellents/">recommended by health authorities</a> and <a href="https://theconversation.com/mozzies-biting-heres-how-to-choose-a-repellent-and-how-to-use-it-for-the-best-protection-150183">apply it</a> to ensure all exposed areas of skin are covered. These products and safe, affordable and effective.<img style="border: none !important; box-shadow: none !important; margin: 0 !important; max-height: 1px !important; max-width: 1px !important; min-height: 1px !important; min-width: 1px !important; opacity: 0 !important; outline: none !important; padding: 0 !important;" src="https://counter.theconversation.com/content/212711/count.gif?distributor=republish-lightbox-basic" alt="The Conversation" width="1" height="1" /></p> <p><a href="https://theconversation.com/profiles/cameron-webb-6736"><em>Cameron Webb</em></a><em>, Clinical Associate Professor and Principal Hospital Scientist, <a href="https://theconversation.com/institutions/university-of-sydney-841">University of Sydney</a></em></p> <p><em>Image credits: Getty Images</em></p> <p><em>This article is republished from <a href="https://theconversation.com">The Conversation</a> under a Creative Commons license. Read the <a href="https://theconversation.com/its-warming-up-and-mozzies-are-coming-heres-how-to-mosquito-proof-your-backyard-212711">original article</a>.</em></p>

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Why mozzies bite some more than others

<p dir="ltr">While summer brings with it days on the beach and nights outside enjoying the balmy weather, another, more unpleasant summer fixture also comes out in droves: mosquitoes.</p> <p dir="ltr">Although some of us dread being covered in itchy bites, there are others who mosquitoes seem to ignore - and now scientists have part of the answer explaining why.</p> <p dir="ltr">Researchers from Rockefeller University have found that mosquitoes are attracted to people based on the smell of their skin, created through a blend of particular acids.</p> <p dir="ltr">Focusing on Aedes aegypti, the mosquito which carries viruses such as dengue, yellow fever and Zika virus, the team used samples of human forearm odour collected on nylon stockings from 64 people, performing more than 2300 tests over 174 days across a three-year study.</p> <p dir="ltr">They found that people who were highly attractive to the mosquitoes had significantly higher levels of carboxylic acids which contribute to their skin odour.</p> <p dir="ltr">These carboxylic acids are produced when bacteria on the skin breaks down steroids and cholesterol secreted by our sweat glands.</p> <p dir="ltr">"We tested mosquito attraction to human skin odour and identified people who are exceptionally attractive or unattractive to mosquitoes," they wrote.</p> <p dir="ltr">"Chemical analysis revealed that highly attractive people produce significantly more carboxylic acids in their skin [than others]."</p> <p dir="ltr">They also noted that there weren’t any chemicals found in higher levels on the skin of less attractive people and argued that this supports the idea that people’s skin lack attractive odours, rather than emitting an odour that repels mosquitoes.</p> <p dir="ltr">As for why some people have higher levels of these chemicals in their skin odour than others, the researchers suggested that genetics may play a role.</p> <p dir="ltr">"Understanding why some humans are more attractive than others provides insights into what skin odorants are most important to the mosquito and could inform the development of more effective ... repellents," they wrote.</p> <p dir="ltr">The study, published in the journal <em><a href="https://doi.org/10.1016/j.cell.2022.09.034" target="_blank" rel="noopener">Cell</a></em>, isn’t the first time scientists have attempted to understand why some people are more attractive to mozzies than others - and there are plenty of reasons why.</p> <p dir="ltr">Mosquito researcher Dr Cameron Webb from the University of Sydney told the <em><a href="https://www.abc.net.au/news/2022-10-19/nt-mosquitoes-study/101548550" target="_blank" rel="noopener">ABC</a></em> it could be to do with genetics, as well as your temperature, your diet, whether you’re sweaty or even whether you’re pregnant.</p> <p dir="ltr">Dr Gordana Rasic, a senior mosquito research officer at QIMR Berghofer Medical Research Institute in Queensland, explained that the factors driving the behaviour of mozzies are “very complex”.</p> <p dir="ltr">"Mosquito brains are small but they still process signals from hundreds and hundreds of different receptors," she said. </p> <p dir="ltr">"Biting humans is specific to female mosquitoes — they need to bite humans and take blood in order to develop their egg and basically reproduce — so it's an absolutely essential instinct."</p> <p dir="ltr">While this study adds a new piece to the puzzle of mozzie behaviour, Dr Webb noted that this study focused on one mosquito species out of thousands of species around the world.</p> <p dir="ltr">"Even if you solve the problem for one mosquito, that doesn't mean the relationship and their willingness to bite people applies to all of the mozzies," he said. </p> <p><span id="docs-internal-guid-07911092-7fff-f285-028e-94767fc3f8aa"></span></p> <p dir="ltr"><em>Image: Getty Images</em></p>

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Tragedy as Aussie boy dies from mosquito bite

<p>A nine-year-old boy from Western Australia has tragically died from dengue fever while on holiday with his family. </p> <p>Glenn Pulgadas had been on holiday with his parents, Glenn and Ryza, in the Philippines to see extended family when he was bitten by a mosquito.</p> <p>According to the <a title="www.abc.net.au" href="https://www.abc.net.au/news/2022-08-30/wa-boy-dies-dengue-fever-in-philippines-warning-travellers/101386032">ABC</a>, the boy began feeling unwell on August 12th and was admitted to hospital. </p> <p>He was described as being “weak in appearance” with headaches, fever, abdominal pain, vomiting and nose bleeds.</p> <p>Glenn then went into dengue shock syndrome which typically includes clamminess, a rapid weak pulse and narrowing of pulse pressure. </p> <p>These symptoms then led to organ failure, with Glenn tragically passing away on August 25th.</p> <p>The young boy is being remembered as "bright and bubbly" by all who knew him.</p> <p>“Glenn was a bright, bubbly, young boy who was so full of life and always had a smile on his face,” said family friend Danielle Zarzycki.</p> <p>Glenn's hometown community of Harvey has launched a <a title="www.gofundme.com" href="https://www.gofundme.com/f/glenn-pulgadas-memorial">GoFundMe</a> page to raise money for funeral expenses which has so far reached more than $9000.</p> <p>One of the top donators, who gave $1,000 to Glenn's family, is local St Anne’s School, where Glenn was a year three student. </p> <p>Dengue fever is spread via the bite of some species of mosquito. </p> <p>Three out of four people who contract dengue won’t even get sick, and for those who do the symptoms can be mild and they often recover in a matter of days.</p> <p>About one in 20 people who become sick with dengue will be hit by a severe form and in the worst cases, the disease can lead to shock, internal bleeding and death. </p> <p><em>Image credits: Facebook</em></p>

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Where do all the mosquitoes go in the winter?

<p>Summer evenings by the pool, lake or BBQ mean mosquitoes. But what about during winter when we’re mostly indoors? As the weather cools, these bloodsucking pests are rarely seen.</p> <p>But where do they go?</p> <p><strong>Warm, wet conditions suit mosquitoes</strong></p> <p>Mosquitoes have complex life cycles that rely on water brought to <a href="https://theconversation.com/hidden-housemates-the-mosquitoes-that-battle-for-our-backyards-59072" target="_blank" rel="noopener">wetlands, flood plains, and water-holding containers</a> by seasonal rainfall. Depending on whether we’re experiencing a summer under the influence of <a href="https://theconversation.com/will-the-arrival-of-el-nino-mean-fewer-mosquitoes-this-summer-102496" target="_blank" rel="noopener">El Niño</a> or <a href="https://theconversation.com/la-nina-will-give-us-a-wet-summer-thats-great-weather-for-mozzies-147180" target="_blank" rel="noopener">La Niña</a>, mosquito populations will change in different ways.</p> <p>During warmer months, their life cycle lasts about a month. Eggs laid around water hatch and the immature mosquitoes go through four developmental stages. Larvae then change to pupae, from which an adult mosquito emerges, sits briefly on the water surface, and then flies off to buzz and bite and continue the cycle.</p> <p>Water is crucial but temperature is really important too. Unlike warm-blooded animals, mosquitoes can’t control their own body temperatures. The warmer it is, the more active mosquitoes will be. There’s usually more of them about too.</p> <p>But once cold weather arrives, their activity slows. They fly less, they don’t bite as often, they reproduce less, and their life cycle takes longer to complete.</p> <p>Temperature also plays a role in determining the ability of mosquitoes to <a href="https://www.frontiersin.org/articles/10.3389/fmicb.2020.584846/full" target="_blank" rel="noopener">spread viruses</a>.</p> <p>Cold weather isn’t great for mosquitoes but <a href="https://www.annualreviews.org/doi/abs/10.1146/annurev-ento-011613-162023" target="_blank" rel="noopener">millions of years of evolution</a> have given them a <a href="https://link.springer.com/article/10.1186/s13071-017-2235-0" target="_blank" rel="noopener">few tricks to survive</a>.</p> <figure class="align-center "><img src="https://images.theconversation.com/files/468677/original/file-20220614-21-qmcj4w.jpg?ixlib=rb-1.1.0&amp;rect=0%2C43%2C4883%2C3211&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px" srcset="https://images.theconversation.com/files/468677/original/file-20220614-21-qmcj4w.jpg?ixlib=rb-1.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=400&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/468677/original/file-20220614-21-qmcj4w.jpg?ixlib=rb-1.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=400&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/468677/original/file-20220614-21-qmcj4w.jpg?ixlib=rb-1.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=400&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/468677/original/file-20220614-21-qmcj4w.jpg?ixlib=rb-1.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=503&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/468677/original/file-20220614-21-qmcj4w.jpg?ixlib=rb-1.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=503&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/468677/original/file-20220614-21-qmcj4w.jpg?ixlib=rb-1.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=503&amp;fit=crop&amp;dpr=3 2262w" alt="" /><figcaption><em><span class="caption">Ponds and puddles may be frozen but that doesn’t mean all mosquitoes have disappeared.</span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/7UYnlgDyf0o" target="_blank" rel="noopener">Tom Keldenich/Unsplash</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/" target="_blank" rel="noopener">CC BY</a></span></em></figcaption></figure> <p><strong>Mosquitoes don’t disappear completely</strong></p> <p>On a sunny afternoon in winter, you may notice the occasional mosquito buzzing about in your backyard. Not as many as in summer but they’re still around.</p> <p>Some mosquitoes do disappear. For example, the activity of the pest mosquito <em>Culex annulirostris</em>, thought to play an important role in the <a href="https://theconversation.com/japanese-encephalitis-virus-has-been-detected-in-australian-pigs-can-mozzies-now-spread-it-to-humans-178017" target="_blank" rel="noopener">spread of Japanese encephalitis virus</a> in Australia, dramatically declines when temperatures start dropping <a href="https://onlinelibrary.wiley.com/doi/10.1111/j.1442-9993.1980.tb01260.x" target="_blank" rel="noopener">below 17.5℃</a>.</p> <p><a href="https://onlinelibrary.wiley.com/doi/10.1111/aen.12021" target="_blank" rel="noopener">Studies in Sydney</a> have shown some mosquitoes, such as <em>Culex annulirostris</em>, disappear. Others, such as <em>Culex quinquefasciatus</em> and <em>Culex molestus</em>, remain active throughout the winter. You just may not notice them (unless they enter your home to buzz about your ears).</p> <figure class="align-center "><img src="https://images.theconversation.com/files/469917/original/file-20220621-17-k6jyri.jpg?ixlib=rb-1.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px" srcset="https://images.theconversation.com/files/469917/original/file-20220621-17-k6jyri.jpg?ixlib=rb-1.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=400&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/469917/original/file-20220621-17-k6jyri.jpg?ixlib=rb-1.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=400&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/469917/original/file-20220621-17-k6jyri.jpg?ixlib=rb-1.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=400&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/469917/original/file-20220621-17-k6jyri.jpg?ixlib=rb-1.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=503&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/469917/original/file-20220621-17-k6jyri.jpg?ixlib=rb-1.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=503&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/469917/original/file-20220621-17-k6jyri.jpg?ixlib=rb-1.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=503&amp;fit=crop&amp;dpr=3 2262w" alt="" /><figcaption><em><span class="caption">Some mosquitoes, such as the common Aedes notoscriptus, may occasionally be seen buzzing about in winter.</span> <span class="attribution"><span class="source">Cameron Webb/NSW Health Pathology</span></span></em></figcaption></figure> <p><strong>Mosquitoes can disappear into diapause</strong></p> <p>We’re familiar with the idea of mammals hibernating through winter but mosquitoes, like many other insects, can enter a phase of inactivity called <a href="https://onlinelibrary.wiley.com/doi/10.1111/eea.12753" target="_blank" rel="noopener">diapause</a>.</p> <p>Once cold weather arrives, adult mosquitoes find hiding places such as tree hollows and animal burrows, within the cracks and crevices of bushland environments, or in garages, basements or other structures around our homes, suburbs and cities. These mosquitoes may only live a few weeks during summer but going into diapause allows them to survive many months through winter.</p> <p>Mosquitoes can also be found in frozen bodies of water, whether it is a bucket of water in your backyard or a near freezing wetland. For example, there is a group of mosquitoes that belong to the genus <em>Coquillettidia</em> whose <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/jvec.12338" target="_blank" rel="noopener">larvae attach</a> to the submerged parts of aquatic plants and can survive the cold winter temperatures. Their development dramatically slows and they’ll stay in the water until spring arrives.</p> <figure class="align-center zoomable"><a href="https://images.theconversation.com/files/469888/original/file-20220621-11-eny4r6.jpg?ixlib=rb-1.1.0&amp;q=45&amp;auto=format&amp;w=1000&amp;fit=clip"><img src="https://images.theconversation.com/files/469888/original/file-20220621-11-eny4r6.jpg?ixlib=rb-1.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;fit=clip" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px" srcset="https://images.theconversation.com/files/469888/original/file-20220621-11-eny4r6.jpg?ixlib=rb-1.1.0&amp;q=45&amp;auto=format&amp;w=600&amp;h=400&amp;fit=crop&amp;dpr=1 600w, https://images.theconversation.com/files/469888/original/file-20220621-11-eny4r6.jpg?ixlib=rb-1.1.0&amp;q=30&amp;auto=format&amp;w=600&amp;h=400&amp;fit=crop&amp;dpr=2 1200w, https://images.theconversation.com/files/469888/original/file-20220621-11-eny4r6.jpg?ixlib=rb-1.1.0&amp;q=15&amp;auto=format&amp;w=600&amp;h=400&amp;fit=crop&amp;dpr=3 1800w, https://images.theconversation.com/files/469888/original/file-20220621-11-eny4r6.jpg?ixlib=rb-1.1.0&amp;q=45&amp;auto=format&amp;w=754&amp;h=503&amp;fit=crop&amp;dpr=1 754w, https://images.theconversation.com/files/469888/original/file-20220621-11-eny4r6.jpg?ixlib=rb-1.1.0&amp;q=30&amp;auto=format&amp;w=754&amp;h=503&amp;fit=crop&amp;dpr=2 1508w, https://images.theconversation.com/files/469888/original/file-20220621-11-eny4r6.jpg?ixlib=rb-1.1.0&amp;q=15&amp;auto=format&amp;w=754&amp;h=503&amp;fit=crop&amp;dpr=3 2262w" alt="" /></a><figcaption><em><span class="caption">By going into ‘diapause’ adults can survive in places like tree hollows for the cold months.</span> <span class="attribution"><a class="source" href="https://images.unsplash.com/photo-1625635756778-218152037ccc?ixlib=rb-1.2.1&amp;ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&amp;auto=format&amp;fit=crop&amp;w=1770&amp;q=80" target="_blank" rel="noopener">Unsplash/Pat Whelan</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/" target="_blank" rel="noopener">CC BY</a></span></em></figcaption></figure> <p><strong>All their eggs in one winter basket</strong></p> <p>Some mosquitoes make it through the winter thanks to their eggs. Mosquito eggs can be incredibly resilient. They survive being dried out in hot and salty coastal wetlands during summer but also frozen in snow-covered creeks in winter.</p> <p>In coastal regions of Australia, eggs of the saltmarsh mosquito (<em>Aedes vigilax</em>), sit perfectly safely on soil. Once the weather warms and tides bring in water to the wetlands, these eggs will be ready to hatch.</p> <p>There is also a special mosquito in Australia known as the “snow melt mosquito” (<em>Aedes nivalis</em>) whose <a href="https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1440-6055.1996.tb01371.x" target="_blank" rel="noopener">eggs survive under snow</a> and hatch once that snow melts and fills ponds, creeks and wetlands throughout alpine regions.</p> <p><strong>Does it matter where mosquitoes go in the winter?</strong></p> <p>It also isn’t just the mosquitoes that survive the cold months. Viruses, such as <a href="https://theconversation.com/japanese-encephalitis-virus-can-cause-deadly-brain-swelling-but-in-less-than-1-of-cases-178985" target="_blank" rel="noopener">Japanese encephalitis virus</a> or <a href="https://theconversation.com/explainer-what-is-ross-river-virus-24630" target="_blank" rel="noopener">Ross River virus</a>, can survive from <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2631767/" target="_blank" rel="noopener">summer to summer</a> in mosquito eggs, immature stages, or diapausing adults.</p> <p>Knowing the seasonal spread of mosquitoes helps health authorities design surveillance and control programs. It may help understand how <a href="https://entomologytoday.org/2022/05/24/snow-covered-tires-help-invasive-mosquitoes-survive-cold-winters/" target="_blank" rel="noopener">invasive mosquitoes survive</a> conditions in Australia outside their native ranges by <a href="https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0211167" target="_blank" rel="noopener">hiding out from the cold</a>, such as in rainwater tanks.</p> <p>Even mosquitoes typically found in tropical locations can even <a href="https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/1365-2664.13480" target="_blank" rel="noopener">adapt to cooler climates</a>.</p> <p>This knowledge may even expose the chilly chink in mosquito’s armour that we can use to better control mosquito populations and reduce the risks of disease outbreaks.<img style="border: none !important; box-shadow: none !important; margin: 0 !important; max-height: 1px !important; max-width: 1px !important; min-height: 1px !important; min-width: 1px !important; opacity: 0 !important; outline: none !important; padding: 0 !important;" src="https://counter.theconversation.com/content/185021/count.gif?distributor=republish-lightbox-basic" alt="The Conversation" width="1" height="1" /></p> <p><em><a href="https://theconversation.com/profiles/cameron-webb-6736" target="_blank" rel="noopener">Cameron Webb</a>, Clinical Associate Professor and Principal Hospital Scientist, <a href="https://theconversation.com/institutions/university-of-sydney-841" target="_blank" rel="noopener">University of Sydney</a></em></p> <p><em>This article is republished from <a href="https://theconversation.com" target="_blank" rel="noopener">The Conversation</a> under a Creative Commons license. Read the <a href="https://theconversation.com/where-do-all-the-mosquitoes-go-in-the-winter-185021" target="_blank" rel="noopener">original article</a>.</em></p> <p><em>Image: Getty Images</em></p>

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The science of Japanese encephalitis

<p>Japanese encephalitis has catapulted seemingly out of nowhere and into Australian headlines in recent days. With the disease having now <a href="https://www.abc.net.au/news/2022-03-09/health-authorities-on-alert-over-japanese-encephalitis-virus/100894208" target="_blank" rel="noreferrer noopener">reached four states and sadly caused two confirmed deaths</a>, many Australians are looking to answer questions about this new-to-us viral infection.</p> <p>So, what is Japanese encephalitis, why is it spreading in Australia now, and is there anything we can do?</p> <p><strong>What is Japanese encephalitis and what causes it?</strong></p> <p>As the name suggests, Japanese encephalitis is a type of encephalitis, or inflammation of the brain. Symptoms of the disease include fever, headache, vomiting and seizures.</p> <p>It’s caused by the Japanese encephalitis virus (JEV), an RNA virus in the Flaviviridae family. Other viruses in this family include dengue virus and <a href="https://cosmosmagazine.com/science/biology/zika-where-did-it-come-from-and-how-can-we-get-rid-of-it/" target="_blank" rel="noreferrer noopener">Zika virus</a>. They are what’s known as arboviruses – short for arthropod-borne viruses, referring to the fact that they are spread by insects like ticks and mosquitoes.</p> <p>Specifically, JEV is spread by mosquitoes in the <em>Culex</em> genus. Pigs and wading birds like herons and egrets are “amplifying hosts”: that means the virus can infect them and replicate to levels high enough that it can go on to infect a mosquito that bites the larger animal.</p> <p>Humans and horses can both be infected by the virus via a mosquito bite, but we are what’s known as “dead-end hosts”: the virus can’t replicate to high enough levels in our blood to transfer to a mosquito if we’re bitten again.</p> <p>Scientists aren’t quite sure of why JEV replicates better in pigs than in humans. Ali Zaid, a viral immunologist from the Menzies Health Research Institute Queensland at Griffith University, says that viruses usually have preferred host species that are best for them to replicate in – which is known as tropism.</p> <p>“There’s most likely something about the cell entry receptors in humans compared to what is in a bird that makes it easier or more difficult for a particular virus to get in,” he says.</p> <p>You can’t catch the virus from another person or by eating pork products from an infected pig. That’s because the route of infection matters. JEV needs to be spread by mosquito bite and particularly to get into the blood – so it can’t do you any harm if you just breathe it in or eat food containing it.</p> <p>The vast majority of JEV infections are asymptomatic – <a href="https://immunisationhandbook.health.gov.au/vaccine-preventable-diseases/japanese-encephalitis" target="_blank" rel="noreferrer noopener">the Australian Immunisation Handbook</a> says that only between 1 in 25 and 1 in 1000 infections actually cause clinical disease.</p> <p>But for those who are unfortunate enough to develop the disease, it’s often very serious. Between 20% and 30% of symptomatic cases are fatal, and 30–50% of people who survive the acute illness experience ongoing neurological symptoms.</p> <p>We’re not really sure what causes some people to have a severe response to JEV infection.</p> <p>Like many viral diseases, the more dangerous symptoms like fever or encephalitis are actually part of our body’s response to the viral infection, not directly caused by the virus itself.</p> <p>“Most of the time the virus will go into its preferred cell, infect it, replicate – and if it has evolved to sort of be sneaky, it will leave the cell relatively unharmed,” says Zaid.</p> <p>“But what happens is the immune system will trigger a knee-jerk reaction, which is designed to brace every other cell in the body against future viral infection. This inflammation is there to essentially kill any cell that may be infected.”</p> <p>Children and older people seem to be more vulnerable. For older adults, that’s probably down to ageing.  </p> <p>“Your immune system ages and it’s less able to fend off an explosive infection, and your organs are less likely to handle the damage and inflammation that results from an immune response against the virus,” says Zaid.</p> <p>Zaid points out that in many other countries where Japanese encephalitis is endemic, it’s primarily a disease of childhood.</p> <p>Australia is a bit of an outlier in only experiencing cases in adults, and also in having a better-resourced health system than many countries in South and Southeast Asia where JEV is more widespread – so it can be difficult to translate knowledge from other parts of the world to our context.</p> <p><strong>Why is Japanese encephalitis spreading in Australia now?</strong></p> <p>Japanese encephalitis has been present in Australia for a while, but largely confined to tropical areas – small corners of the Cape York Peninsula and the Torres Strait. Vaccination programs instituted following the first recorded outbreak in the Torres Strait in 1995 have provided protection for humans, and Queensland health department mosquito control activities helped keep the disease, if not the virus itself, largely at bay in those areas.</p> <p>For Nigel Beebe, an associate professor at the University of Queensland and CSIRO working on several mosquito-borne diseases including JEV and malaria, the current spread to the south is unfortunate but not exactly surprising.</p> <div class="newsletter-box"> <p class="h2">Get an update of science stories delivered straight to your inbox.</p> <div id="wpcf7-f6-p184886-o1" class="wpcf7" dir="ltr" lang="en-US" role="form"> <div class="screen-reader-response"> </div> <form class="wpcf7-form mailchimp-ext-0.5.56 spai-bg-prepared init" action="/health/medicine/japanese-encephalitis-explainer/#wpcf7-f6-p184886-o1" method="post" novalidate="novalidate" data-status="init"> <p style="display: none !important;"><span class="wpcf7-form-control-wrap referer-page"><input class="wpcf7-form-control wpcf7-text referer-page spai-bg-prepared" name="referer-page" type="hidden" value="https://cosmosmagazine.com/" data-value="https://cosmosmagazine.com/" aria-invalid="false" /></span></p> <p><!-- Chimpmail extension by Renzo Johnson --></form> </div> </div> <p>“We have been thinking that this was going to happen since around 2000,” he says.</p> <p>“In Australia we have access to wading birds that fly in from Papua New Guinea, we have a large feral pig population – so they’re both amplifying hosts – and we have a very good mosquito vector.”</p> <p>That vector is <em>Culex annulirostrus</em>, or the common banded mosquito – a freshwater mosquito found widely across the eastern half of Australia, as well as in Papua New Guinea. Beebe says the species has been shown to be able to transmit JEV in laboratory studies.</p> <p>His lab is currently working on population genetics to try to identify different strains of <em>C.</em> <em>annulirostrus </em>and understand whether they have different capacity to transmit viruses. There are other flaviviruses that are already present in these regions and transmitted by local <em>Culex</em> mosquitoes.  </p> <p>Several experts have suggested that climate change and Australia’s recent weather conditions could have tipped the balance in favour of the virus’s southwards spread.</p> <p>“The reports of multiple cases of Japanese encephalitis acquired in Australia occurring at the same time as severe flooding serves as a warning of the significant potential for new human health threats associated with climate change, including the emergence of new pathogens and the appearance of known infections in new localities,” says Karin Leder, a professor in the School of Public Health and Preventive Medicine at Monash University.</p> <p>The current La Niña cycle has likely influenced migration of birds that carry the virus and increased the abundance of mosquitoes. Rain and flooding can create wetland environments in new places, which draw birds and mosquitoes together and potentially bring them into closer contact with both humans and pigs.</p> <p>“Regardless of La Niña, if our climate is to become warmer, and challenged by flood events, we may find that JEV will circulate widely and continuously,” says Gregor Devine, group leader of the Mosquito Control Laboratory at QIMR Berghofer.</p> <p><strong>What can we do to protect ourselves and each other?</strong></p> <p>Unfortunately, there are no specific treatments for Japanese encephalitis, but that doesn’t mean we’re powerless against the virus.</p> <p>There are two vaccines against JEV currently approved for use in Australia, and they’re both highly effective.</p> <p>Both are based on the same strain of JEV and derived from virus grown in a cultured cell line developed from African green monkey cells. <a href="https://cosmosmagazine.com/health/assessing-the-various-vaccine-technologies/" target="_blank" rel="noreferrer noopener" data-type="URL" data-id="https://cosmosmagazine.com/health/assessing-the-various-vaccine-technologies/">The major difference</a> is that one vaccine (Imojev) contains a live attenuated virus, and the other (JEspect) contains an inactivated virus.</p> <p><a href="https://immunisationhandbook.health.gov.au/vaccine-preventable-diseases/japanese-encephalitis" target="_blank" rel="noreferrer noopener">According to the Australian Immunisation Handbook</a>, a single dose of Imojev generates protective levels of neutralising antibodies against four strains of JEV in 85% of adults, and about 65% of adults maintain these protective antibodies against at least three strains five years after vaccination. Young children maintain protective antibodies for at least 12 months after a single dose. The vaccine is approved for use in people aged nine months and older in Australia.</p> <p>JEspect is delivered as two primary doses, like most COVID-19 vaccines. It’s approved for use in people aged two months and older, with a smaller dose being used for children aged two months to three years. At least 83% of adults have protective levels of neutralising antibodies six months after vaccination with two doses of JEspect, and 48% maintain these levels after two years. Protection also remains high in children for at least six months. JEspect can also be used as a booster if there is a high ongoing risk of JEV infection.</p> <p>“Those are some of the best vaccines we’ve got,” says Zaid. “They work quite well and they’re available. They’re not cheap, that’s the only problem.”</p> <p>The Victorian state government has recently flagged that it wants to make JEV vaccines more broadly accessible, given the current outbreak.</p> <p>Zaid agrees that this should be considered, especially for people who are exposed to areas with both mosquitoes and animal hosts like pigs and wading birds.</p> <p>He also points out that, while Japanese encephalitis is in the news, many strategies to reduce the risk of JEV infection will also help counter other mosquito-borne flaviviruses such as Murray Valley encephalitis and Kunjin virus (a West Nile strain). These are already established in southern Australia, they’re also likely to increase with the current favourable mosquito breeding conditions – and we don’t have <a href="https://cosmosmagazine.com/health/developing-vaccines-for-forgotten-flaviviruses/" target="_blank" rel="noreferrer noopener">vaccines for them</a>.</p> <p>Targeting the mosquitoes, rather than the virus, then, is a worthwhile strategy. That includes taking extra care to avoid mosquito bites by applying strong insect repellent and eliminating pools of stagnant water that promote mosquito breeding.</p> <p>Avoiding the outdoors at dusk and dawn, when mosquitoes are most active, and wearing long, light-coloured clothing (mosquitoes are attracted to dark colours) also help.</p> <p>There are also strategies to control the mosquito population, like insecticides that kill larvae – but they can be difficult and expensive to implement over a broad area, especially when weather conditions favour the mosquitoes.</p> <p>Beebe says that the affected states have come together effectively to deliver a coordinated health response to JEV; in addition to that, he’d like to see the creation of national centre of disease control.</p> <p>“There’s a lot to learn now if Japanese encephalitis is going to stay on mainland Australia and continually cycle,” he says. “We really need to work out its ecology in our particular landscape.”</p> <p><!-- Start of tracking content syndication. Please do not remove this section as it allows us to keep track of republished articles --></p> <p><img id="cosmos-post-tracker" style="opacity: 0; height: 1px!important; width: 1px!important; border: 0!important; position: absolute!important; z-index: -1!important;" src="https://syndication.cosmosmagazine.com/?id=184886&amp;title=The+science+of+Japanese+encephalitis" width="1" height="1" data-spai-target="src" data-spai-orig="" data-spai-exclude="nocdn" /></p> <p><!-- End of tracking content syndication --></p> <div id="contributors"> <p><em><a href="https://cosmosmagazine.com/health/medicine/japanese-encephalitis-explainer/" target="_blank" rel="noopener">This article</a> was originally published on <a href="https://cosmosmagazine.com" target="_blank" rel="noopener">Cosmos Magazine</a> and was written by <a href="https://cosmosmagazine.com/contributor/matilda-handlsey-davis" target="_blank" rel="noopener">Matilda Handsley-Davis</a>. Matilda is a science writer at Cosmos. She holds a Bachelor of Arts and a Bachelor of Science (Honours) from the University of Adelaide.</em></p> <p><em>Image: Getty Images</em></p> </div>

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Can mosquitos spread coronavirus?

<p>The pathogens mosquitos spread by sucking our blood cause over half a million deaths each year and hundreds of millions of cases of severe illness.</p> <p>But there is no scientific evidence to suggest mosquitos are transmitting SARS-CoV-2, the virus that causes COVID-19.</p> <p>While there are many things we have yet to know about the coronavirus, current research supports that it’s highly unlikely a mosquito will pick up the virus by biting an infected person, let alone be able to pass it on.</p> <p>Mosquitos CAN transmit other viruses</p> <p>Female mosquitos need the nutrition found in blood to help develop their eggs. Viruses take advantage of this requirement as mosquitoes can easily move from host to host to transmit diseases.</p> <p>But for a mosquito to become infected, it first needs to bite an infected animal, such as a bird of kangaroo, or a person.</p> <p>The list of diseases a mosquito can transfer includes dengue, tallow fever, chikungunya, Zika and Ross River virus. They can also spread malaria, which is caused by a parasite.</p> <p>But they cannot transmit other viruses such as HIV and Ebola.</p> <p>Coronavirus is mainly spread through droplets produced when people sneeze or cough, and by touched surfaces that are contaminated.</p> <p>While the virus is found in blood, there’s no evidence that can spread via mosquitos.</p> <p>So if a mosquito does pick up a substantial dose of the virus, the virus won’t be able to infect the mosquito itself.</p> <p>And if the mosquito isn’t infected, it won’t be able to transmit it to the next person.</p>

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Can mosquitoes spread coronavirus?

<p>The pathogens mosquitoes spread by sucking our blood cause over <a href="https://www.who.int/malaria/en/">half a million deaths each year</a> and <a href="https://www.who.int/news-room/fact-sheets/detail/dengue-and-severe-dengue">hundreds of millions of cases of severe illness</a>.</p> <p>But there is no scientific evidence to suggest mosquitoes are transmitting SARS-CoV-2, the virus that causes COVID-19.</p> <p>There is <a href="https://cmr.asm.org/content/20/4/660">much more to learn about the coronavirus</a> but based on current understandings, it’s highly unlikely a mosquito will pick up the virus by biting an infected person, let alone be able to pass it on.</p> <p><strong>Yes, mosquitoes can transmit other viruses</strong></p> <p>Female mosquitoes need the nutrition contained in blood to help develop their eggs. Viruses take advantage of this biological requirement of mosquitoes to move from host to host.</p> <p>But for a mosquito to become infected, it first needs to bite an infected animal, such as a bird or kangaroo, or a person.</p> <p>Mosquitoes can transmit a number of viruses, including dengue, yellow fever, chikungunya, Zika and Ross River virus. They can also transmit malaria, which is caused by a parasite.</p> <p>But they can’t transmit many other viruses, including HIV and Ebola.</p> <p>For <a href="https://europepmc.org/article/med/10554479">HIV</a>, mosquitoes themselves don’t become infected. It’s actually unlikely a mosquito will pick up the virus when it bites an infected person due to the low concentrations of the HIV circulating in their blood.</p> <p>For Ebola, <a href="https://www.ajtmh.org/content/journals/10.4269/ajtmh.1996.55.89">even when scientists inject the virus into mosquitoes</a>, they don’t become infected. One study collected tens of thousands of insects during an Ebola outbreak but <a href="https://academic.oup.com/jid/article/179/Supplement_1/S148/880615">found no virus</a>.</p> <p><strong>No, not coronavirus</strong></p> <p>The new coronavirus is <a href="https://www.who.int/news-room/commentaries/detail/modes-of-transmission-of-virus-causing-covid-19-implications-for-ipc-precaution-recommendations">mostly spread via droplets produced when we sneeze or cough</a>, and by touching <a href="https://theconversation.com/we-know-how-long-coronavirus-survives-on-surfaces-heres-what-it-means-for-handling-money-food-and-more-134671">contaminated surfaces</a>.</p> <p>Although coronavirus has been <a href="https://www.tandfonline.com/doi/full/10.1080/22221751.2020.1729071">found in blood samples from infected people</a>, there’s no evidence it can spread via mosquitoes.</p> <p>Even if a mosquito did pick up a high enough dose of the virus in a blood meal, there is no evidence the virus would be able to infect the mosquito itself.</p> <p>And if the mosquito isn’t infected, it won’t be able to transmit it to the next person she bites.</p> <p><strong>Why some viruses and not others?</strong></p> <p>It’s easy to think of mosquitoes as tiny flying dirty syringes transferring droplets of infected blood from person to person. The reality is far more complex.</p> <p>When a mosquito bites and sucks up some blood that contains a virus, the virus quickly ends up in the gut of the insect.</p> <p>From there, the virus needs to infect the cells lining the gut and “escape” to infect the rest of the body of the mosquito, spreading to the legs, wings, and head.</p> <p>The virus then has to infect the salivary glands before being passed on by the mosquito when it next bites.</p> <p>This process can take a few days to over a week.</p> <p>But time isn’t the only barrier. The virus also has to negotiate getting out of the gut, getting through the body, and then into the saliva. Each step in the process can be an impenetrable barrier for the virus.</p> <p>This may be straightforward for viruses that have adapted to this process but for others, the virus will perish in the gut or be excreted.</p> <p><span><a href="https://theconversation.com/profiles/cameron-webb-6736"><em>Cameron Webb</em></a><em>, Clinical Associate Professor and Principal Hospital Scientist, <a href="https://theconversation.com/institutions/university-of-sydney-841">University of Sydney</a></em></span></p> <p><em>This article is republished from <a href="https://theconversation.com">The Conversation</a> under a Creative Commons license. Read the <a href="https://theconversation.com/can-mosquitoes-spread-coronavirus-134898">original article</a>.</em></p>

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Why mosquitoes prefer to bite some people over others

<p>It’s always you, isn’t it? The person busy swatting away buzzing backyard mosquitoes or nursing an arm full of itchy red lumps after a weekend camping trip.</p> <p>You’re not imagining it – mosquitoes really are attracted to some people more than others.</p> <p><strong>Why do mosquitoes need blood?</strong></p> <p>Only female mosquitoes bite. They do it for the nutrition contained in blood, which helps develop their eggs.</p> <p>Mosquitoes don’t just get blood from people. They’re actually far more likely to get it from biting animals, <a href="https://theconversation.com/how-australian-wildlife-spread-and-suppress-ross-river-virus-107267">birds</a>, <a href="https://www.abc.net.au/news/2016-08-18/australian-geographic-nature-photographer-of-the-year-winners/7753248">frogs</a> and reptiles. They even <a href="https://www.nature.com/articles/s42003-018-0096-5">bite earthworms</a>.</p> <p>But some mosquitoes specifically target people. One of the worst culprits is the <em>Aedes aegypti</em> species, which spreads <a href="https://www.cdc.gov/dengue/index.html">dengue</a> and <a href="https://www.cdc.gov/yellowfever/">yellow fever</a> viruses.</p> <p>Another that prefers humans are the <em>Anopheles</em> mosquitoes, responsible for spreading the parasites that cause <a href="https://www.who.int/malaria/en/">malaria</a>.</p> <p><strong>How do mosquitoes find us?</strong></p> <p>Most mosquitoes will get their blood from whatever is around and don’t necessarily care if they’re biting one person or another.</p> <p>Although it’s our blood they’re after, there is no strong indicator they prefer a particular blood type over another. Some studies have <a href="https://academic.oup.com/jme/article/41/4/796/885285">suggested they prefer people with type O blood</a> but that’s unlikely to be the case for all types of mosquitoes.</p> <p>Whether we’re picked out of a crowd may come down to heavy breathing and skin smell.</p> <p>When they need blood, mosquitoes can pick up on the <a href="https://www.cambridge.org/core/journals/bulletin-of-entomological-research/article/role-of-carbon-dioxide-in-hostfinding-by-mosquitoes-diptera-culicidae-a-review/2506B86EF63852B2D02EC3FCEE1E3B8B">carbon dioxide</a> we exhale. Around the world, carbon dioxide is one of the most common “baits” used to attract and collect mosquitoes. If you’re exhaling greater volumes of carbon dioxide, you’re probably an easier target for mosquitoes.</p> <p>When the mosquito gets closer, she is <a href="https://www.sciencedirect.com/science/article/pii/S2214574517300342">responding to a range of stimuli</a>.</p> <p>Perhaps it’s <a href="https://www.sciencedirect.com/science/article/abs/pii/S1471492210002618">body heat and sweat</a>: exercise that increases body temperature and perspiration can attract mosquitoes.</p> <p>Perhaps it’s body size: studies indicate <a href="https://academic.oup.com/trstmh/article/96/2/113/1909983">pregnant women are more likely to be bitten</a> by mosquitoes.</p> <p>How hairy are you? Mosquitoes may have a tough job finding a path through to your skin if there is an abundance of body hair.</p> <p>More than anything else, though, it’s about the smell of your skin. Hundreds of chemicals are sweated out or emitted by our body’s bacteria. The <a href="https://www.sciencedirect.com/science/article/pii/S2214574517300536">cocktail of smells they create</a> will either attract or deter mosquitoes.</p> <p><strong>It’s not just who they bite but where</strong></p> <p>Mosquitoes could also have a preference for different parts of the body.</p> <p>One study showed mosquitoes are more attracted to hands and feet <a href="https://www.nature.com/articles/srep27141">than armpits</a>, but that just turned out to be because of deodorant residues.</p> <p>Mosquitoes may also be more attracted to our feet: studies have shown cheese sharing similar bacteria to that <a href="https://www.ncbi.nlm.nih.gov/pubmed/15275226">found between our toes</a> attracts mosquitoes!</p> <p><strong>Who is to blame for this misery?</strong></p> <p>It’s not your diet. There is no evidence that what you eat or drink will prevent mosquito bites. Some food or drink may subtly change how many mosquitoes are likely to bite you but it won’t make that much difference.</p> <p><a href="https://www.mdpi.com/2075-4450/9/4/129">Eating bananas</a> or <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2832015/">drinking beer</a> has been shown to marginally increase the attraction of mosquitoes but the results aren’t enough to suggest any dietary change will reduce your mosquito bites. That’s why our supermarket shelves aren’t full of “mozzie repellent” pills.</p> <p>Your irresistibility to mosquitoes may not be your fault. Blame your parents. Studies have shown the chemicals responsible for the “<a href="https://europepmc.org/article/med/2230769">skin smell</a>” that attracts mosquitoes has <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4406498/">a high level of heritability</a> when twins are exposed to biting mosquitoes.</p> <p><strong>What can you do about it?</strong></p> <p>We have to be careful about generalisations. There are thousands of types of mosquitoes around the world and all will have a different preference for what or who to bite. And the attraction of individuals and the scenario that plays out in one part of the world may be much different in another.</p> <p>Remember, it only takes one mosquito bite to transmit a pathogen that could make you sick. So whether you’re a mosquito magnet or feeling a little invisible because you’re not bitten so often, don’t be complacent and <a href="https://theconversation.com/the-best-and-worst-ways-to-beat-mosquito-bites-70274">use insect repellents</a>.<!-- Below is The Conversation's page counter tag. Please DO NOT REMOVE. --><img style="border: none !important; box-shadow: none !important; margin: 0 !important; max-height: 1px !important; max-width: 1px !important; min-height: 1px !important; min-width: 1px !important; opacity: 0 !important; outline: none !important; padding: 0 !important; text-shadow: none !important;" src="https://counter.theconversation.com/content/128788/count.gif?distributor=republish-lightbox-basic" alt="The Conversation" width="1" height="1" /><em><!-- End of code. If you don't see any code above, please get new code from the Advanced tab after you click the republish button. The page counter does not collect any personal data. More info: http://theconversation.com/republishing-guidelines --></em></p> <p><em><a href="https://theconversation.com/profiles/cameron-webb-6736">Cameron Webb</a>, Clinical Lecturer and Principal Hospital Scientist, <a href="https://theconversation.com/institutions/university-of-sydney-841">University of Sydney</a></em></p> <p><em>This article is republished from <a href="http://theconversation.com">The Conversation</a> under a Creative Commons license. Read the <a href="https://theconversation.com/feel-like-youre-a-mozzie-magnet-its-true-mosquitoes-prefer-to-bite-some-people-over-others-128788">original article</a>.</em></p>

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6 things that make you more attractive to mosquitoes

<p>The pesky mosquito – is there anything more annoying at a BBQ? For many of us, the answer is “no”, but for others, mozzies don’t seem to be an issue at all – but why? Why do mozzies favour come people over others? It may be because of these six things about you which they simply can’t get enough of.</p> <p><strong>1. You exhale a lot of carbon dioxide</strong></p> <p>Larger people (and pregnant women) produce more carbon dioxide. Incredibly, <a href="https://www.cambridge.org/core/journals/bulletin-of-entomological-research/article/role-of-carbon-dioxide-in-hostfinding-by-mosquitoes-diptera-culicidae-a-review/2506B86EF63852B2D02EC3FCEE1E3B8B" target="_blank"><strong><span style="text-decoration: underline;">this makes them more attractive to mozzies</span></strong></a> and thus more likely to be bitten. If that’s not incentive to lose some weight, we don’t know what is!</p> <p><strong>2. You’re hot</strong></p> <p>No, really, you are! <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0122716" target="_blank"><strong><span style="text-decoration: underline;">A 2015 study</span></strong></a> found that having a high body temperature increases the likelihood of being bitten by mosquitoes. Again, this only makes it harder for overweight people, who as a rule have a higher body temperature. Our advice? Stay cool!</p> <p><strong>3. You have type O blood</strong></p> <p>It’s not just the blood bank that wants your type O. In 2004, <a href="https://www.ncbi.nlm.nih.gov/pubmed?Db=pubmed&amp;Cmd=ShowDetailView&amp;TermToSearch=15311477&amp;ordinalpos=3&amp;itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVDocSum" target="_blank"><strong><span style="text-decoration: underline;">researchers discovered</span></strong></a> that people with type O blood had a significantly higher chance of being bitten by mozzies than those with type A. But take this one with a grain of salt – the study’s sample size was small and it hasn’t been repeated since.</p> <p><strong>4. The bacteria on your skin make you smell good</strong></p> <p>Well, they make you smell good to the mozzies – not necessarily to the person sitting next to you. <a href="http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0028991" target="_blank"><strong><span style="text-decoration: underline;">Researchers found</span></strong></a> that the microbes that live on the skin produce certain chemicals which make you smell more attractive to those flying pests.</p> <p><strong>5. You’ve just exercised</strong></p> <p>While being overweight makes you more susceptible to mozzie bites, so does exercise. Not only does it raise your body temperature (see above), but it also <a href="http://science.sciencemag.org/content/161/3848/1346" target="_blank"><strong><span style="text-decoration: underline;">increases lactic acid production</span></strong></a>, which is secreted through the skin, attracting mosquitoes.</p> <p><strong>6. You’re a beer drinker</strong></p> <p>It might be time to switch to soft drink – that cold brew isn’t doing you any favours. In 2002, <a href="https://www.ncbi.nlm.nih.gov/pubmed/12083361" target="_blank"><strong><span style="text-decoration: underline;">Japanese scientists found</span></strong></a> that even one glass of an alcoholic beverage (beer in particular) makes you more attractive to mozzies, but no one is quite sure why this is.</p> <p>So, if you’re an overweight, exercise-loving, germy, beer-drinking person with type O blood, you should probably invest in some high-strength insect repellent!</p>

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Why mosquitoes bite some people more than others

<p>Anyone that has ever been to a BBQ, ever, knows about the frustration mosquito bites. The only more frustrating thing about those lumps then their itchiness it turning to your partner to complain about them, only to discover they don’t have a single bite. Turns out, there’s a science behind it.</p> <p><a href="https://www.plos.org/wp-content/uploads/2013/05/pone-10-4-Fernandez-Grandon.pdf" target="_blank"><em><span style="text-decoration: underline;"><strong>The authors of a new study</strong></span></em></a> explored the differences in attraction of skin odors to mosquitoes in a group of (brave) volunteers drawn from a group of identical and non-identical twins.</p> <p>The test subjects put their hands into a specially constructed plexi-glass sealed dome where the odors either attract or repel 20 female mosquitoes without being allowed to bite. Sure enough the identical twins, who share all their genes, had consistently more similar scores compared to fraternal twins – therefore showing a clear genetic component in mosquito attractiveness.</p> <p>However, Joe Conlon, PhD, technical advisor to the American Mosquito Control Association says "Researchers are just beginning to scratch the surface," </p> <p>Scientists do now know that genetics account for a whopping 85 per cent of our susceptibility to mosquito bites. However, they've also identified certain elements of our body chemistry that, when found in excess on the skin's surface, make mosquitoes swarm closer.</p> <p><strong>So who do mosquitoes like more?</strong></p> <p>Being overweight or obese, drinking alcohol or doing exercise all raise your metabolic rate, making you more attractive to mozzies. They are also believed to be attracted to other chemicals that can reside on the skin and carbon dioxide. This means that pregnant women and adults are more prone than children.</p> <p><strong>How can you stop it?</strong></p> <p>Mosquitoes are attracted to movement, so if you’re someone to dance up a storm, gesture wildly or even try to wave mosquitoes off, you may be making yourself more susceptible. This is because mosquitoes don’t actually see that well, so you are making yourself more visible. They also have difficulty seeing light colored clothing and flying near fans.</p> <p>Or, a good old repellent will do.</p> <p><strong>Related links:</strong></p> <p><span style="text-decoration: underline;"><em><strong><a href="http://www.oversixty.co.nz/health/body/2015/12/6-signs-you-need-more-sleep/">6 signs you need more sleep</a></strong></em></span></p> <p><span style="text-decoration: underline;"><em><strong><a href="http://www.oversixty.co.nz/news/news/2016/01/side-sleeping-avoid-neurological-disease/">Your sleep position linked to diseases</a></strong></em></span></p> <p><span style="text-decoration: underline;"><em><strong><a href="http://www.oversixty.co.nz/news/news/2015/12/women-have-a-harder-time-sleeping-than-men/">Why do women have a harder time sleeping than men?</a></strong></em></span></p>

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Why mosquitoes are more attracted to some people

<p>There's no doubt we're in the midst of mosquito season and if you’re finding you’re getting bitten left right and centre, while the person next to you manages to escape bite-free, there’s a reason for it – and it’s not because the mozzies have a personal vendetta against you.</p> <p>Dr Cameron Webb, Principal Hospital Scientist and Clinical Lecturer, told The Huffington Post Australia, “Some people are definitely more likely to suffer a mosquito bite than others.”</p> <p>He added, “But it's not just the number of bites that vary from person to person. Each individual will react to a mosquito bite differently. In the same way we all differ in our reaction to food, chemical or environmental allergens, we all differ in our reaction to the saliva mozzies inject when they feed.”</p> <p>So what is it about a person that makes them so delicious to mosquitoes?</p> <p>“Mosquitoes target in on individuals based on a range of factors. First and foremost, it is the carbon dioxide we exhale. That signals to the mosquitoes that there is a warm-blooded animal about,” explained Webb.</p> <p>“Secondly, it is the chemical cocktail of smelly substances on our skin that determines how frequently we’ll be bitten by mosquitoes. The mix of these 300 or so chemical compounds on our skin attracts (or sometimes repels) mosquitoes.</p> <p>"Blood type may play a role but there is certainly not a blood type mosquitoes will completely ignore. Probably the best natural repellent is a thick covering of body hair!"</p> <p>But if you do want to escape the unbearable itchy sensation, Webb recommends looking for products containing DEET.</p> <p>"The insect repellents that provide the longest lasting protection are those that contain 'DEET' or 'picaridin'. They’re commonly found in all the popular brands found on supermarket shelves. Make sure they’re applied as a thin and even coat on all exposed skin, as a dab ‘here and there’ won’t provide adequate protection,” he advised. </p> <p><strong>Related links: </strong></p> <p><strong><em><a href="http://www.oversixty.co.nz/news/news/2015/12/former-housekeeper-to-queen-reveals-secrets/">Former housekeeper to the Queen reveals her secrets</a></em></strong><br /><br /><strong><em><a href="http://www.oversixty.co.nz/news/news/2015/12/laundry-room-space-ideas/">Simple ideas to get more space out of laundry room</a></em></strong><br /><br /><strong><em><a href="http://www.oversixty.co.nz/news/news/2015/12/cleaning-tricks-for-people-who-hate-doing-chores/">14 cleaning tricks for people who hate doing chores</a></em></strong></p> <p> </p>

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