Why does the mosquito change its track and fly towards skin???  How does it detect our skin?  What are the odors from skin that it detects? And can we block the mosquito skin odor sensors and reduce attractiveness?

Recent research done by scientists at the University of California, Riverside can now help address these questions.  They report on Dec. 5 in the journal Cell that the very receptors in the mosquito’s maxillary palp that detect carbon dioxide are ones that detect skin odors as well, thus explaining why mosquitoes are attracted to skin odor — smelly socks, worn clothes, bedding — even in the absence of CO2.

Until now, which mosquito olfactory neurons were required for attraction to skin odor remained a mystery.  The new finding — that the CO2-sensitive olfactory neuron is also a sensitive detector of human skin — is critical not only for understanding the basis of the mosquito’s host attraction and host preference, but also because it identifies this dual receptor of CO2 and skin-odorants as a key target that could be useful to disrupt host-seeking behavior and thus aid in the control of disease transmission.

Next, using a chemical computational method they developed, the researchers screened nearly half a million compounds and identified thousands of predicted ligands. They then short-listed 138 compounds based on desirable characteristics such as smell, safety, cost and whether these occurred naturally. Several compounds either inhibited or activated cpA neurons of which nearly 85 percent were already approved for use as flavor, fragrance or cosmetic agents. Better still, several were pleasant-smelling, such as minty, raspberry, chocolate, etc., increasing their value for practical use in mosquito control.

“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.  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.”

Currently, CO2 is the primary lure in mosquito traps. Generating CO2 requires burning fuel, evaporating dry ice, releasing compressed gas or fermentation of sugar — all of which is expensive, cumbersome, and impractical for use in developing countries.  Compounds identified in this study, like cyclopentanone, offer a safe, affordable and convenient alternative that can finally work with surveillance and control traps.