Why Mosquitoes Think We’re Delicious

Most mosquitoes will drink any mammalian blood but the species Aedes aegypti – the ones that bring the world Zika, dengue, and yellow fever — have evolved to bite humans exclusively. Researchers from Princeton think they know why.

It starts in the brain, says Carolyn “Lindy” McBride, an assistant professor of ecology and evolutionary biology and neuroscience. “We sort of dove into the brain of the mosquito and asked, ‘What can you smell? What lights up your brain? What’s activating your neurons? And how is your brain activated differently when you smell human odor versus animal odor?’”

Setting up the experiment was complicated. First they had to genetically engineer mosquitos whose brains lit up when active, then deliver human- flavored air and non-human animal aromas into custom-built imaging equipment. The human volunteers did not shower for a few days to get pungent, then stripped naked and lay in Teflon bags while their scents wafted to the mosquitoes. They had to be nude because clothing fibers – cotton, polyester, what-have-you – have their own smells and would’ve distorted the data.

Mosquito brains have 60 distinct nerve centers, most of which the researchers assumed would play a role in zeroing in on the Homo sapien flavor. But only two were active: one that discerned both human and other smells and one that detected humans only. Apparently we have a “citrusy” scent.

“The simplicity surprised us,” says McBride. “Despite the complexity of human odor, and the fact that it doesn’t really have any kind of human-specific compounds in it, the mosquitoes have evolved a surprisingly simple mechanism for recognizing us.”

The result of the research (which was years in the making) appears in the journal Nature.

Photo credit: Princeton University