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Researchers are trying to understand how mosquitoes can home in on humans from hundreds of yards away. Two groups of scientists are going about it in two somewhat different ways, but they're coming to similar conclusions. And their findings could someday mean an end to malaria, a mosquito-borne disease that kills about a million people a year.
NPR's Joanne Silberner reports.
JOANNE SILBERNER: Biology Professor Larry Zwiebel of Vanderbilt University has a big challenge.
Professor LAURENCE ZWIEBEL (Biology, Vanderbilt University): It's hard to ask a mosquito what she smells.
SILBERNER: It's her sense of smell that brings her to her prey - her, because male mosquitoes don't bite humans. Zwiebel figures the answer to what a mosquito smells starts with her nose, which is located at the end of her antenna.
Prof. ZWIEBEL: We're taking the mosquito nose, parts of it, the active, molecular components and actually putting them into systems in the lab that allow us to play with them, to find out what they respond to and ultimately to find out how we can muck them up.
SILBERNER: The system he's using is not mosquitoes, but frog eggs. He's loading the frog eggs with mosquito genes that construct any of the 72 odor detectors in mosquitoes' noses. When he exposes the frog eggs to a test odor, sensors attached to the eggs will go off if the odor is one a mosquito would recognize, that is, if it matches the receptor. Zwiebel has just published his work in the online version of the Proceedings of the National Academy of Sciences.
John Carlson at Yale University has the same idea, but instead of using frog eggs to determine what mosquitoes can smell, he's using the workhorse of a lot of labs: Fruit flies - again, isolating the genes that are the blueprints for mosquitoes' noses. Then he transplants those genes into fruit flies.
Professor�JOHN CARLSON (Biology, Yale University): Then we systematically test, with a whole panel of different odors, and see which odors cause that receptor to fire, that is, make a strong response. We have this hooked up to a loudspeaker, so we get a whole lot of noise if we get the right odor.
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SILBERNER: That's what happens when a fruit fly that's gotten a specific gene transplant from a mosquito encounters a specific sweet-smelling chemical found in fruit and wine. Carlson published a study earlier this month in the journal Nature that describes some of the other things his lab has found.
Prof.�CARLSON: We identified a number of receptors that responded very strongly to compliments of human odor, and we think that some of these may act in the process of human recognition. That is, they may be able to help the mosquito figure out that there's a person out there and help the mosquito navigate towards us and which eventually leads to biting us and in many cases transmitting a disease to us.
SILBERNER: The human and chemical odors Carlson has found that attract mosquitoes are pretty much the same as what Zwiebel has found. Both groups are working with labs in the Netherlands and Africa on the next questions: Can you use some of the smells you know mosquitoes recognize to lure them into traps? Or is there a way to stop up the mosquitoes' noses so they can't find what they really want, which is us?
Joanne Silberner, NPR News.
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