There are few winners in the climate crisis, but scientists are sure there will be at least one: mosquitoes.
These insects – annoying at best, deadly at worst – thrive in heat and humidity. As climate change leads to more frequent and severe heat waves, as well as storms and floods that leave behind pools of stagnant water in which most breed, what we see is the mosquito boom.
For the first time in decades, the US Centers for Disease Control and Prevention (CDC) is warning of multiple locally acquired cases of malaria in the United States — news that has put mosquitoes in the spotlight.
Scientists warn that malaria could become more common in the US as temperatures rise.
This has raised new concerns about mosquitoes invading regions where they haven’t been for generations – if ever – and what that could mean for the spread of the deadly diseases they carry.
Rising temperatures allow mosquitoes to grow faster and live longer. Whereas before they would die during harsh winters in many places, they now have a better chance of surviving longer to increase their populations. Heat also speeds up the time it takes for a parasite or virus to mature inside a mosquito.
“The hotter the temperature gets, the shorter the process becomes. So not only do these mosquitoes live longer, they also become potentially infectious sooner,” said Oliver Brady, associate professor at the London School of Hygiene and Tropical Medicine.
They also get other benefits from the heat. When it’s warmer, more people tend to go out in the morning and late afternoon – prime time for mosquitoes.
The heat is also prompting cities to increase their amount of green space, which has a vital cooling effect but could also provide ideal new breeding grounds for bloodsucking insects.
In the United States, the number of “mosquito days” — the ones with the warm, humid conditions they love — has increased across the country, according to a recent analysis by Climate Central, a nonprofit research group.
The researchers analyzed data spanning more than four decades from nearly 250 sites and found that over 70% of them had become more hospitable to mosquitoes.
While most of the approximately 200 mosquito species in the US are harmless, there are about a dozen that can transmit diseases to humans, including chikungunya, dengue, Zika and West Nile virus.
While serious mosquito-borne illnesses remain rare in the United States, other countries are not so lucky.
In sub-Saharan Africa, where malaria has had devastating consequences, climate change is helping mosquitoes significantly expand their range, according to recent research.
Anopheles mosquitoes, which carry malaria, on average, have moved to higher altitudes by about 6.5 meters per year and southwards by nearly 5 kilometers per year, according to a report by Georgetown University.
It’s a pace that tracks climate change and could have significant consequences for areas that have never had malaria before and are likely not prepared, said Colin Carlson, a global change biologist at Georgetown University and co-author of the report.
Dengue is another potentially deadly disease that is expected to increase in a warmer world. The disease causes fever, nausea, vomiting, fatigue and diarrhea and, in some cases, internal bleeding and leads to death. There is no specific cure or treatment for dengue, leaving sufferers little choice but to cope with the symptoms.
Peru is currently grappling with the worst mosquito-borne dengue outbreak on record, which has infected nearly 150,000 people and killed more than 250.
Experts said exceptionally high levels of rain and heat provided ideal conditions for the mosquitoes. While scientists have yet to assess the role climate change played in the outbreak, Carlson said the links appear clear.
“I’m not a betting man, but I would bet money when we were going to do this study, which would be climate change,” he said.
Now dengue is knocking on the door of Europe and the United States.
“A billion new people will be exposed to weather conditions suitable for dengue transmission, and most of these people are in Western Europe, the United States and temperate China,” said Carlson.
There have been locally spread outbreaks in Texas, Florida, Hawaii and Arizona. And last week, the European Center for Disease Prevention and Control warned that the Aedes albopictus species – which can transmit dengue and chikungunya – is moving north and west across Europe as climate change hits the continent from fastest warming in the world.
“What is surprising is the speed of spread,” Celine Gossner, ECDC’s lead expert on emerging and vector-borne diseases, told the CNN . In just a decade, the number of regions where this mosquito establishes itself has tripled, she said.
Even with this new exposure, however, the US and Europe are unlikely to see major outbreaks or large numbers of deaths from the dengue virus.
“The future change story is really more about big increases in areas that already have dengue, which are going to get much worse,” Brady said. He singled out China and parts of India as particularly at risk.
“This is a really scary situation because a huge number of people live in these areas and even small changes can be potentially catastrophic,” he said.
Communities that are already on the front lines of the climate crisis will always be the hardest hit by mosquito-borne disease, and that’s where investment should be directed, said Shannon LaDeau, a disease ecologist at the Cary Institute of Ecosystems Studies.
But the shift of mosquito-borne diseases to regions like the US and Europe is yet to come as a shock.
“People living in the temperate zone will see their way of life change dramatically because they never had to worry about it before,” LaDeau told CNN .
The climate crisis is not just an advantage for mosquitoes. Some places may simply be getting too hot.
“There is a threshold after which the chemistry in your body just doesn’t work anymore,” LaDeau said. The bad news is that these places will likely get too hot for humans too.
Much remains unknown about how mosquitoes will react to the climate crisis. The relationship between climate change and disease is complex, Gossner said.
We know a lot about how temperature changes mosquitoes’ ability to transmit disease, little about how quickly mosquitoes are moving to new places, and very little about whether overall mosquito populations are growing, Carlson said.
Scientists are working to develop tools that can better assess the link between mosquito-borne diseases and climate change.
In the meantime, there are ways people can protect themselves from the risk, including using repellents, putting screens on windows and doors, and getting rid of any standing water from places like flower pots and gutters.
Scientists are also working on high-tech methods to reduce populations. A project in Florida is testing a genetically engineered mosquito designed to pass on a lethal gene that kills female mosquitoes – the ones that bite.
Other experiments involve the use of the wolbachia bacteria, which can prevent viruses from replicating inside a mosquito, making them less likely to transmit viruses.
There are also vaccines on the horizon for diseases such as dengue fever and malaria. “This is a really big deal,” Carlson said. But whether they will be shared equitably around the world is another question, she added.
“It’s a long way to try to understand the best way to use these tools. But there is a lot of hope on the horizon,” said Brady.
Ultimately, tackling climate change will have a huge impact.
The path the world takes to reduce planet-warming pollution will lead to very different futures for mosquito-borne diseases, Brady said. “Aggressive mitigation [climática] would be by far the least risk.”
Source: CNN Brasil
Bruce Belcher is a seasoned author with over 5 years of experience in world news. He writes for online news websites and provides in-depth analysis on the world stock market. Bruce is known for his insightful perspectives and commitment to keeping the public informed.
