Rising Temperatures Will Help Mosquitos Infect a Billion More People
By Marlene Cimons
Mosquitoes are unrelenting killers. In fact, they are among the most lethal animals in the world. When they carry dangerous viruses or other organisms, a bite can be unforgiving. They cause millions of deaths every year from such infectious diseases as malaria, dengue, Zika, chikungunya, yellow fever and at least a dozen more.
But here's the really bad news: climate change is expected to make them even deadlier. As the planet heats up, these insects will survive winter and proliferate, causing an estimated billion or more new infections by the end of the century, according to new research.
"Plain and simple, climate change is going to kill a lot of people," said biologist Colin J. Carlson, a postdoctoral fellow in Georgetown University's biology department, and co-author of the study, published in the journal PLOS Neglected Tropical Diseases. "Mosquito-borne diseases are going to be a big way that happens, especially as they spread from the tropics to temperate countries."
The study predicted an amenable climate could prompt some of these new cases within regions not previously regarded as vulnerable, including the U.S. These viruses can result in volatile outbreaks when conditions are right, as was the case with Zika. "We've known about Zika since 1947, and we watched it slowly spread around the world until 2015, when it arrived in Brazil and suddenly we had an explosive epidemic on our hands," Carlson said.
"Chikungunya has done something not too different from that," he added. "These viruses proliferate quickly in populations that don't have any immunity — and we're very scared about that. If you only have one month that's warm enough for outbreaks, the question is: 'how much damage you can do…?' For viruses like these, it's a lot."
The study underscores the growing evidence that climate change is having — and will continue to have — a deleterious impact on global health, not only from the direct effects of extreme weather events like heat waves and flooding, but also because mosquitoes thrive in warm temperatures and carbon dioxide, encouraging them to flourish and spread disease. Rising temperatures also are causing many to migrate to new locations.
"This is a very important forward-looking report," said Robert T. Schooley, an infectious diseases expert at the University of California, San Diego, and editor of the journal Clinical Infectious Diseases, who was not involved in this study. "Understanding in as much detail as possible the risks we face as we move toward a warmer planet is essential. Mosquitoes are able to spread blood-borne pathogens faster than epidemiologists can track an epidemic. There are many one-way doors through which we will go as the planet warms. The spread of mosquitoes and other vectors that can transmit multiple pathogens is an important one that those who don't think climate change is a serious problem should ponder."
The research team, also led by Sadie J. Ryan, of the University of Florida's emerging pathogens institute and associate professor of medical geography, looked what would happen to the two most common disease-carrying mosquitoes, Aedes aegypti and Aedes albopictus, as temperatures increase during the coming decades. It found that global warming will expose almost all of the world's population to mosquitoes at some point in the next 50 years. Also, there likely will be year-round transmissions in the tropics and seasonal risks almost everywhere else, along with a greater intensity of infections, according to the study. Moreover, shorter, warmer winters will mean more mosquitoes will survive.
"Where the number of temperature-suitable months of the year increase, so too will the winter months decrease, lowering the threshold for overwintering survival of the mosquitoes," Ryan said. "We already have evidence, for example, in New England, that tire piles can provide sufficiently ambient overwintering habitat already for albopictus, by virtue of retaining pooled water that doesn't get too cold. With fewer months at those very low temperatures, the pressure on survival is lessened, and more overwintering mosquitoes will make it to the next season."
Humidity and water are crucial for vector breeding.
The scientists' goal was to better understand what increasing temperatures would mean for the handful of viruses that Aedes mosquitoes spread. "We used a model of virus spread at different temperatures to mark out where in the world these viruses might be over time, and used climate models to map people at risk now and in the future, that is, 2050 and 2080," Carlson explained. "This study is a bit of a numbers game: with 7 billion people on Earth, who's most at risk now? Who's at risk in a generation? We don't know where mosquitoes will be in the future. What we can do is say where they might be able to transmit viruses if they show up."
The burden on developing countries, already hard hit, likely will increase, especially in the East African portion of sub-Saharan Africa, "one of the top regions to experience increases in people at risk," Ryan said. "These are regions in which we tend to focus on malaria and malaria control … However, we know that there is also dengue circulating in these regions. It is essential to think about surveillance of these diseases now. This is a part of the world that will be facing the intersection of multiple vulnerabilities under climate change, with underfunded infrastructure to manage multiple health impacts."
Regions most impacted by Dengue worldwide, 2015.
Dengue, which causes high fever, headache, and joint pain, is the most common vector-borne viral disease in the world, with up to 100 million infections and 25,000 deaths annually, and, in recent years, has appeared in the U.S. It caused an epidemic in Hawaii in 2001, as well as a cluster of cases in Florida about ten years ago, with additional sporadic infections since then. It also has shown up with increasing frequency along the Texas-Mexican border.
The 2009 Florida cases, in fact, were the first dengue cases acquired in the continental U.S. — outside of the Texas-Mexico border — since 1945, and the first locally transmitted cases in Florida since 1934. "We've seen dengue showing up in Hawaii and Florida, then we saw Zika arrive in Florida and really grab public attention," Ryan said. "Because Aedes aegypti is such a globalized mosquito, the potential for it to facilitate new outbreaks of many diseases is high."
Often, cases that arise in the U.S. typically result after Americans travel and are infected abroad. Once they return home, a local mosquito bites them and acquires the virus. It then can transmit it to others. "Travelers overseas can bring back pathogens that can establish in local mosquito populations," Ryan said. "This potential is a very real issue."
Estimated potential range of Aedes aegypti and Aedes albopictus in the U.S. Maps do not represent risk for spread of disease, 2017.
There are several thousand species of mosquitoes, but only a few transmit disease. Anopheles mosquitoes carry the parasites that causes malaria and filariasis — also called elephantiasis — and the virus that causes encephalitis. Culex mosquitoes carry encephalitis, filariasis, and the virus that causes West Nile, while the two Aedes species studied in this paper transmit the viruses that cause yellow fever, dengue and encephalitis.
"We've only managed to capture the uncertain futures for two mosquitoes that spread a handful of diseases — and there's at least a dozen vectors we need this information on," Carlson said. "It's very worrisome to think how much these diseases might increase, but it's even more concerning that we don't have a sense of that future. We have several decades of work to do in the next couple years if we want to be ready."
He believes that climate mitigation could save millions of lives, "but I also don't want us to fall into the trap of mitigating climate change just to keep dengue and Zika in the tropics, and out of the U.S. and Europe," he said. "Facing something as massive as climate change gives us a chance to rethink the world's health disparities, and work towards a future where fewer people die of preventable diseases like these. Facing climate change and tackling the burden of neglected tropical diseases go hand-in-hand."
Reposted with permission from our media associate Nexus Media.
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1. Stay Informed<p>A first order of business in pet evacuation planning is to understand and be ready for the possible threats in your area. Visit <a href="https://www.ready.gov/be-informed" target="_blank">Ready.gov</a> to learn more about preparing for potential disasters such as floods, hurricanes, and wildfires. Then pay attention to related updates by tuning <a href="http://www.weather.gov/nwr/" target="_blank">NOAA Weather Radio</a> to your local emergency station or using the <a href="https://www.fema.gov/mobile-app" target="_blank">FEMA app</a> to get National Weather Service alerts.</p>
2. Ensure Your Pet is Easily Identifiable<p><span>Household pets, including indoor cats, should wear collars with ID tags that have your mobile phone number. </span><a href="https://www.avma.org/microchipping-animals-faq" target="_blank" rel="noopener noreferrer">Microchipping</a><span> your pets will also improve your chances of reunion should you become separated. Be sure to add an emergency contact for friends or relatives outside your immediate area.</span></p><p>Additionally, use <a href="https://secure.aspca.org/take-action/order-your-pet-safety-pack" target="_blank" rel="noopener noreferrer">'animals inside' door/window stickers</a> to show rescue workers how many pets live there. (If you evacuate with your pets, quickly write "Evacuated" on the sticker so first responders don't waste time searching for them.)</p>
3. Make a Pet Evacuation Plan<p> "No family disaster plan is complete without including your pets and all of your animals," says veterinarian Heather Case in <a href="https://www.youtube.com/watch?v=Q9NRJkFKAm4" target="_blank">a video</a> produced by the American Veterinary Medical Association.</p><p>It's important to determine where to take your pet in the event of an emergency.</p><p>Red Cross shelters and many other emergency shelters allow only service animals. Ask your vet, local animal shelters, and emergency management officials for information on local and regional animal sheltering options.</p><p>For those with access to the rare shelter that allows pets, CDC offers <a href="https://www.cdc.gov/healthypets/emergencies/pets-in-evacuation-centers.html" target="_blank">tips on what to expect</a> there, including potential health risks and hygiene best practices.</p><p>Beyond that, talk with family or friends outside the evacuation area about potentially hosting you and/or your pet if you're comfortable doing so. Search for pet-friendly hotel or boarding options along key evacuation routes.</p><p>If you have exotic pets or a mix of large and small animals, you may need to identify multiple locations to shelter them.</p><p>For other household pets like hamsters, snakes, and fish, the SPCA recommends that if they normally live in a cage, they should be transported in that cage. If the enclosure is too big to transport, however, transfer them to a smaller container temporarily. (More on that <a href="https://www.spcai.org/take-action/emergency-preparedness/evacuation-how-to-be-pet-prepared" target="_blank" rel="noopener noreferrer">here</a>.)</p><p>For any pet, a key step is to establish who in your household will be the point person for gathering up pets and bringing their supplies. Keep in mind that you may not be home when disaster strikes, so come up with a Plan B. For example, you might form a buddy system with neighbors with pets, or coordinate with a trusted pet sitter.</p>
4. Prepare a Pet Evacuation Kit<p>Like the emergency preparedness kit you'd prepare for humans, assemble basic survival items for your pets in a sturdy, easy-to-grab container. Items should include:</p><ul><li>Water, food, and medicine to last a week or two;</li><li>Water, food bowls, and a can opener if packing wet food;</li><li>Litter supplies for cats (a shoebox lined with a plastic bag and litter may work);</li><li>Leashes, harnesses, or vehicle restraints if applicable;</li><li>A <a href="https://www.avma.org/resources/pet-owners/emergencycare/pet-first-aid-supplies-checklist" target="_blank">pet first aid kit</a>;</li><li>A sturdy carrier or crate for each cat or dog. In addition to easing transport, these may serve as your pet's most familiar or safe space in an unfamiliar environment;</li><li>A favorite toy and/or blanket;</li><li>If your pet is prone to anxiety or stress, the American Kennel Club suggests adding <a href="https://www.akc.org/expert-advice/home-living/create-emergency-evacuation-plan-dog/" target="_blank" rel="noopener noreferrer">stress-relieving items</a> like an anxiety vest or calming sprays.</li></ul><p>In the not-unlikely event that you and your pet have to shelter in different places, your kit should also include:</p><ul><li>Detailed information including contact information for you, your vet, and other emergency contacts;</li><li>A list with phone numbers and addresses of potential destinations, including pet-friendly hotels and emergency boarding facilities near your planned evacuation routes, plus friends or relatives in other areas who might be willing to host you or your pet;</li><li>Medical information including vaccine records and a current rabies vaccination tag;</li><li>Feeding notes including portions and sizes in case you need to leave your pet in someone else's care;</li><li>A photo of you and your pet for identification purposes.</li></ul>
5. Be Ready to Evacuate at Any Time<p>It's always wise to be prepared, but stay especially vigilant in high-risk periods during fire or hurricane season. Practice evacuating at different times of day. Make sure your grab-and-go kit is up to date and in a convenient location, and keep leashes and carriers by the exit door. You might even stow a thick pillowcase under your bed for middle-of-the-night, dash-out emergencies when you don't have time to coax an anxious pet into a carrier. If forecasters warn of potential wildfire, a hurricane, or other dangerous conditions, bring outdoor pets inside so you can keep a close eye on them.</p><p>As with any emergency, the key is to be prepared. As the American Kennel Club points out, "If you panic, it will agitate your dog. Therefore, <a href="https://www.akc.org/expert-advice/home-living/create-emergency-evacuation-plan-dog/" target="_blank" rel="noopener noreferrer">pet disaster preparedness</a> will not only reduce your anxiety but will help reduce your pet's anxiety too."</p>
Evacuating Horses and Other Farm Animals<p>The same basic principles apply for evacuating horses and most other livestock. Provide each with some form of identification. Ensure that adequate food, water, and medicine are available. And develop a clear plan on where to go and how to get there.</p><p>Sheltering and transporting farm animals requires careful coordination, from identifying potential shelter space at fairgrounds, racetracks, or pastures, to ensuring enough space is available in vehicles and trailers – not to mention handlers and drivers on hand to support the effort.</p><p>For most farm animals, the Red Cross advises that you consider precautionary evacuation when a threat seems imminent but evacuation orders haven't yet been announced. The American Veterinary Medical Association has <a href="https://www.avma.org/resources/pet-owners/emergencycare/large-animals-and-livestock-disasters" target="_blank">more information</a>.</p>
Bottom Line: If You Need to Evacuate, So Do Your Pets<p>As the Humane Society warns, pets left behind in a disaster can easily be injured, lost, or killed. Plan ahead to make sure you can safely evacuate your entire household – furry members included.</p>
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