Climate change upping the ante in fight against disease-carrying mosquitoes
Columbus and other cities routinely spray for mosquitoes. It helps keep the pests at bay and limit disease, but climate change appears poised to make the job of fighting the biters more difficult.
It's 3:30 am, and Jon Phillips is just starting his day. For most of the year, Phillips works as a school teacher. But he's spent the last 36 summers with Columbus Public Health driving a pickup truck, spraying for mosquitoes.
“They say like what you do, you never work a day in your life. So far, I've never worked a day in my life,” Phillips said.
Columbus Public Health routinely sprays for mosquitoes. The department sets traps across the city and selects neighborhoods based on insect counts and the detection of communicable disease.
“The one we're going today, actually the trap itself hit positive last week for West Nile virus," Phillips said. "There's not a trapping area in Columbus in the last six years that has not hit positive.”
West Nile virus was first detected in the U.S. in 1999 and quickly spread across the country in just a few years. The potentially deadly virus makes its way to humans mainly through the bite of the female Northern House Mosquito, Culex pipiens, which carries the virus after feeding on infected birds.
Ryan Younge oversees the vector control program at Columbus Public Health. He said getting rid of standing water is crucial to preventing mosquitoes from propagating.
“It could be something like the neighbor next door has a pool they're not taking care of, or a pond, or they've got bird baths or saucers underneath their flowerpots. So we always use 'tip, toss and turn,'" Younge said.
Ohio has not had any reported human cases of West Nile so far this year, but 2018 was particularly bad, with 65 human cases and eight deaths statewide. Younge said climate change seems to be making things worse.
“I'm seeing earlier springs, warmer winters, and then we're actually seeing the season go later. We used to be cold at the end of September. Now, September tends to be a lot warmer, so our mosquito season is expanding and we're seeing mosquitoes a lot longer," Younge said.
Megan Meuti, PhD is an entomology professor at Ohio State University. She said her grad students have collected mosquitoes that have fed on blood as late in the season as December and as early as March.
“Now, at that point, they're it's probably too cold for them to like lay eggs or for those larvae to hatch, but that was really surprising," she said.
The midwest is also getting wetter, receiving 42% more rainfall than it did in the 1950s, according to the most recent National Climate Assessment. More rain means more chances for scattered pools of water in which mosquitoes can lay their eggs.
Predicting how much climate change could impact mosquito populations is tricky, Meuti said. There are still too many unknowns.
“It's probably going to be good for some insects, probably the ones that we don't like, honestly, like mosquitoes, and bad for good insects that we really like, like pollinators,” Meuti said.
The good news is researchers are figuring out inventive ways of keeping mosquitoes in check. Professor Meuti explains that in the wintertime, mosquitoes don't die. They hide and go into a hibernation-like state called diapause.
“Before they go into their hibernation state, they pack on fat just like bears do. And they're able to tolerate the low temperatures of winter. And then when it warms up during the spring, that's the cue that they use to know that winter is over," Meuti said.
Using a technique called RNA interference, Meuti and her team were able to break the circadian clock that governs the bugs' behavior, "tricking" them into not biting.
While she doesn't feel bad about killing mosquitoes in her lab, Meuti said she also can't help but admire them.
"They're so small and they seem so insignificant, but they do all the things that we do. They grow and develop, they reproduce, they find their way around, they find food, they have such a dramatic change from being like these little worm-like things that wriggle through the water in their larval stage to pupating to emerging as the adults we know and loathe,” she said.
Meuti doubts we'll ever be able to eradicate mosquitos entirely, even if we wanted to. Instead, she hopes new mosquito control methods will help us live alongside the bloodsuckers while addressing current and emerging threats of disease.
Just don't forget the insect repellent at your next summer barbecue.