Breakthrough Study Shows How Mosquitoes Smell Us, May Lead To Better Repellants

Brett Smith for – Your Universe Online
Many a pleasant summer’s evening has been ruined by the onset of swarms of mosquitoes, and studies have shown that the flying pests are drawn to both the carbon dioxide we exhale and the scent of our skin.
A new study, published in the journal Cell, has found that mosquitoes actually use the same olfactory mechanism to detect both carbon dioxide and skin odors.
“It was a real surprise when we found that the mosquito’s CO2 receptor neuron, designated cpA, is an extremely sensitive detector of several skin odorants as well, and is, in fact, far more sensitive to some of these odor molecules as compared to CO2,” said Anandasankar Ray, an associate professor of entomology at The University of California, Riverside. “For many years we had primarily focused on the complex antennae of mosquitoes for our search for human-skin odor receptors, and ignored the simpler maxillary palp organs.”
To discover that cpA plays a role in detecting human odor, the researchers chemically shut down the activity of the receptor neuron in Aedes aegypti, a species of mosquito known to spread dengue fever. The researchers then looked to see the mosquito’s reaction to human foot odor and found their attraction was greatly reduced, compared to a control group.
The study team also screened nearly half a million compounds to identify several that block and trigger cpA neurons. The researchers noted two chemicals in particular: ethyl pyruvate, a fruity-scented cpA blocker used as a flavor agent in food and cyclopentanone, a minty-smelling cpA trigger used as a flavor and fragrance agent. The cpA-inhibitor ethyl pyruvate was found to substantially lessen the mosquito’s attraction to a human arm. The cpA-trigger cyclopentanone, on the other hand, readily attracting mosquitoes to a trap set up by the study team.
“Such compounds can play a significant role in the control of mosquito-borne diseases and open up very realistic possibilities of developing ways to use simple, natural, affordable and pleasant odors to prevent mosquitoes from finding humans,” Ray said. “Odors that block this dual-receptor for CO2 and skin odor can be used as a way to mask us from mosquitoes. On the other hand, odors that can act as attractants can be used to lure mosquitoes away from us into traps.”
“These potentially affordable ‘mask’ and ‘pull’ strategies could be used in a complementary manner, offering an ideal solution and much needed relief to people in Africa, Asia and South America – indeed wherever mosquito-borne diseases are endemic,” Ray added. “Further, these compounds could be developed into products that protect not just one individual at a time but larger areas, and need not have to be directly applied on the skin.”
Conventional mosquito traps use carbon dioxide to attract mosquitoes, but generating the gas is expensive, cumbersome, and impractical in developing countries.
“The powerful experimental approaches we have developed will help us find potential solutions that we could use not only here in the United States but also in Africa, Asia, and South America, where affordability is key in the war against these diseases,” Ray concluded.