How mosquitoes smell human sweat (and new ways to stop them)

 Female mosquitoes are known to rely on an array of sensory information to find people to bite, picking up on carbon dioxide, body odor, heat, moisture, and visual cues. Now researchers reporting in the journal Current Biology on March 28 have discovered how mosquitoes pick up on acidic volatiles found in human sweat.

The key is an olfactory coreceptor known as Ir8a. Mosquitoes lacking a functional version of the Ir8a gene were much less attracted to people, the researchers found. The findings potentially suggest new approaches for designing new and improved mosquito repellents.

"Removing the function of Ir8a removes approximately 50 percent of host-seeking activity," says senior author Matthew DeGennaro, a mosquito neurobiology researcher at Florida International University in Miami. "Odors that mask the IR8a pathway could be found that could enhance the efficacy of current repellents like DEET or picaridin. In this way, our discovery may help make people disappear as potential hosts for mosquitoes."

On the flip side, the Ir8a pathway also could be used to design new mosquito attractants, he adds. Those attractants could lure mosquitoes away from people and into traps.

The inspiration for the new work came from previous work DeGennaro conducted as a postdoctoral student in Leslie Vosshall's lab at The Rockefeller University. In those studies, the team disrupted another olfactory coreceptor, called Orco, and watched to see how it changed mosquitoes' behavior.

They found that those mosquitoes had more trouble telling the difference between people and other animals. The mosquitos also lost their interest in nectar and their aversion to DEET. But, they still were attracted to vertebrate animals including people. It meant that there were more receptors still to find.

In the new study, DeGennaro and his colleagues looked to another group of receptors broadly known as ionotropic receptors and specifically Ir8a, which is expressed in the antenna. They used the CRISPR/Cas9 gene-editing system to disrupt Ir8a in Aedes aegypti mosquitoes. Then, they tested the coreceptor's relative contribution in human odor detection and its genetic interaction with other olfactory receptor pathways that had been implicated previously in Ae. aegypti host-seeking behavior.

source :science daily