Can we trick mosquitoes so they stop biting us?
By Jennifer Larson
Ohio State Insights
You and the summertime pest that feeds on your flesh have a lot in common when it comes to feeling sleepy.
Blame (or thank) your internal biological clock. That clock affects your circadian rhythms by controlling your body’s production of a hormone called melatonin, which makes you feel sleepy. The result is an ongoing pattern of sleepiness and alertness.
But did you know that even lowly mosquitoes have circadian rhythms, too?
And as it turns out, scientists such as Ohio State entomologist Megan Meuti, PhD, have been able to tinker with the circadian rhythms in one type of mosquito. By altering those mosquitoes’ circadian rhythms, scientists have learned they can “trick” those mosquitos into getting their seasons mixed up.
They can convince a mosquito that it’s winter — and time to hibernate — when it’s actually summer and time to reproduce.
“The potential for manipulating their seasonal responses may be a very good way of controlling them,” said Meuti, an assistant professor in The Ohio State University College of Food, Agricultural and Environmental Sciences.
What that means for you: Researchers have begun to tap into ways to potentially manipulate the mosquito population in the future, reducing the chances that you’ll get bitten as soon as you walk out of your house in the summer.
How she beat the clock
You probably know the Culex pipiens by a more familiar name: the Northern house mosquito.
This mosquito species is closely associated with West Nile virus in Ohio. These mosquitoes bite birds infected by the virus and then spread it when they bite humans afterward.
But even when they don’t spread West Nile virus, those mosquitoes and the swollen, itchy red lumps they leave behind on your skin are annoying. Combine that annoying factor with the potential to spread disease, and a lot of people have long hoped for a way to reduce the mosquito population. They’ve tried chemical sprays, but unfortunately, many mosquitoes eventually develop resistance to them.
That’s where Meuti’s research comes in.
In her lab, Meuti employed a technique called RNA interference. She injected several thousand Culex pipiens mosquitoes with double-stranded RNA.
(RNA stands for ribonucleic acid, which can serve as a messenger, carrying genetic information from the DNA inside an organism’s cells and allowing it to be made into the proteins that do all the work.)
The double-stranded RNA that she injected into the mosquitoes prevented a specific protein that governs the mosquitoes’ circadian rhythms from being made.
Then Meuti waited. She hoped to see if reducing the amount of a circadian clock proteins had any effect on the mosquitoes’ ability to measure seasonal time. Specifically, she wanted to see if she could convince a mosquito that it was winter when it was really summer — and vice versa.
“Overwintering mosquitoes look different from summer mosquitoes,” she explained. “They have more fat, like a bear does when it hibernates. ”MEGAN MEUTI, OHIO STATE ENTOMOLOGIST
“Overwintering mosquitoes look different from summer mosquitoes,” she explained. “They have more fat, like a bear does when it hibernates. So you measure the fat.”
Winter mosquitoes also contain smaller, undeveloped eggs, since their bodies are devoting most of their resources to survival instead of reproduction.
After about a week, Meuti dissected the mosquitoes. She extracted and measured their body fat, and then she examined their eggs.
Her technique worked.
When she was able to suppress three of the core circadian clock genes, the mosquitoes that should have gone into hibernation behaved like it was summer.
“They were skinny, and they had really big eggs,” she said. “But when I knocked down another gene that was associated with the clock, I saw the opposite effect: Mosquitoes that were reared under long day, summer-like conditions actually behaved like it was winter and had lots of fat and small eggs.”
No more bug spray?
Meuti’s research shows it’s possible to manipulate mosquitoes and trick them into behaving differently. And that could pave the way for researchers to develop strategies to fool large numbers of mosquitoes.
“Mosquitoes are way more complex and sophisticated than we give them credit for,” she said. “And the more we understand their basic biology, the more weapons we’re going to have in our arsenal to better control them.”
Right now, it’s too early to predict what those mechanisms would look like. But Meuti speculated that a potential method could entail putting double-stranded RNA that’s been specifically tailored to affect only a particular species of mosquito in standing water. (She recently gave a talk about what that could look like.)
“So it might be possible in the future that we could sprinkle or spread some double-stranded RNA into the ponds where the larval mosquitoes are living, rather than spraying insecticides,” she said.