AUDIE CORNISH, HOST:
This is the sound of the most dangerous animal in the world.
(SOUNDBITE OF MOSQUITO BUZZING)
CORNISH: The mosquito carries diseases that kill and sicken millions of people every year. Scientists want to understand what draws mosquitoes to humans to figure out new ways to defeat them. And as NPR's Nell Greenfieldboyce reports, they've just discovered how mosquitoes smell human sweat.
NELL GREENFIELDBOYCE, BYLINE: Before mosquitoes can bite us, they've got to find us.
MATTHEW DEGENNARO: It takes multiple cues to get a mosquito really interested in a human.
GREENFIELDBOYCE: Matthew DeGennaro is a scientist at Florida International University. He says, first, from a distance, a mosquito senses carbon dioxide in a person's breath - that draws it closer.
DEGENNARO: After the carbon dioxide, then it begins to sense human odor.
GREENFIELDBOYCE: The mosquito follows that odor, and when it gets really close, it registers body heat and lands on your skin.
DEGENNARO: They actually can taste your skin with their legs. And then they look for a place to bite.
GREENFIELDBOYCE: He was interested in the odor part of this story. What is it about humans' smell that attracts mosquitoes? He and some colleagues genetically altered mosquitoes. They disabled a certain smell receptor in the insect's antenna and found that female mosquitoes were no longer attracted to a key chemical in humans sweat, lactic acid.
What's more, they did lab tests that involved people sticking their hands into a special device. Mosquitoes could fly through a tube to get closer, though not close enough to bite. Mosquitoes with a disabled olfactory receptor were much less likely to home in on human flesh.
DEGENNARO: We found that they had an approximately 50 percent reduction in attraction.
GREENFIELDBOYCE: The results are reported in the journal Current Biology. Lindy McBride is a mosquito researcher at Princeton University. She says the results are exciting.
LINDY MCBRIDE: Finally we have evidence that there's some sort of pathway in the sense of smell that is required for mosquitoes to like us.
GREENFIELDBOYCE: She says it may seem like a no-brainer that messing with a mosquito's sense of smell would make it hard for them to sniff out humans, but mosquitoes actually smell in a couple of different ways.
MCBRIDE: Previously when we took away a different smell pathway, it had no effect, and it was a big surprise.
GREENFIELDBOYCE: She says, now that it's clear how they smell us, researchers could create new kinds of repellents or create irresistibly smelly traps that would lure mosquitoes to their doom. Nell Greenfieldboyce, NPR News.
(SOUNDBITE OF DZIHAN AND KAMIEN'S “AY, AY, AY”)
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