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Climate Change Offers More Ideal Days For Mosquitoes In Louisville

Matt Vanderpool, a Louisville Department of Health and Wellness entomologist who’s spent the last 22 years battling Louisville’s mosquitoes.

Standing in a thicket of wetland woods beside a church in Newburg, entomologist Matt Vanderpool attaches the finishing touches on a mosquito trap. A purple glow lures the mosquitoes in, a bit like a bug zapper. 

“Mosquitoes drink nectar from flowers and the black light mimics the light that’s reflected off of flowers that the pigment in mosquitoes' eyes can see,” he said. 

For the last 22 years, Vanderpool’s work at Louisville’s Department of Health and Wellness battling the city’s mosquitoes. The department runs a mosquito control program designed to identify mosquito-borne diseases, and keep the population in check. 

But that population may be growing as a result of climate change. Kentucky is becoming warmer and wetter, and it’s increasing the number of ideal days for mosquitoes.

The planet’s foremost experts on climate change say global temperatures will rise at least 2.7 degrees Fahrenheit over the next 30 years — even if we take action now to reduce our reliance on fossil fuels.   

Jen Brady, a senior data analyst with the non-profit research group Climate Central, said warming temperatures have already increased the number of days ideal for mosquitoes. 

“For a lot of the country, that range, which is about 73 degrees to 93 degrees, is increasing, the number of days in that range is increasing,” Brady said. 

Louisville already has nearly two more weeks with ideal temperatures for mosquitoes each year than it did in the '80s, Brady said.


And that in turn creates the potential for increased disease transmission. 

Part of Vanderpool’s work with Louisville’s Department of Health and Wellness is to collect mosquitoes so they can be ground up and their RNA tested for diseases including West Nile virus. The department uses the data to decide where and when to spray pesticides, and inform residents about potential threats. 

This year they’ve already found mosquitoes infected with West Nile virus in at least eight zip codes in Jefferson County: 40203, 40206, 40208, 40210 40205, 40212, 40214 and 40215. 

West Nile virus has been present in the U.S. since about 2002, brought here by birds following their migration paths, Vanderpool said. Mosquitoes actually prefer sucking blood from birds rather than humans, he said. 

“They’re not looking to you and I for food. Only the females bite people and the reason the females bite people is because they need that protein in our blood to be able to produce eggs. But both males and females drink the nectar out of flowers,” Vanderpool said. 

West Nile virus is always present in the mosquito population in Louisville, though it rarely infects humans. In fact in the last two years, the U.S. Centers for Disease Control and Preventionhasn’t recorded any human infections in the entire state. 

The CDC says most people who catch the virus don’t feel sick, and only about 1 in 150 people who are infected have severe symptoms, though it can be fatal. 

That’s why Vanderpool recommends taking simple precautions like wearing insect repellant and removing standing water near your house, to limit their breeding habitat. 

He said the solution isn't to remove all the mosquitoes, not that they could if they wanted to. 

“Number one it’s not possible, number two, you're going to end up causing more problems in the grand scheme of things,” Vanderpool said. 

Mosquitoes, after all, are an important source of food for fish and insects and birds, and they’re also pollinators

So as we adapt to a warmer climate, we’ll also have to learn to live with more mosquitoes.

Ryan Van Velzer is the Kentucky Public Radio Managing Editor. Email Ryan at rvanvelzer@lpm.org.