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How mosquitoes smell the sweat

It is actually very difficult to attract mosquitoes.

Maybe it does not feel like it on a warm and stuffy summer night. But every time a mosquito stalks an animal thousand times as big that it's being fed, it's trying to do something extremely dangerous, said Matthew DeGennaro, a mosquito geneticist and a professor at Florida International University. The right signals – a breath of exhaled carbon dioxide, heat, a bit of body odor, other mysterious elements of animal odor – must be present, or mosquitoes do not take the risk.

Traps that could attract mosquitoes Scientists would like to know how to pick up on these clues. In an article published in Current Biology on Thursday, Dr. DeGennaro and colleagues have solved some of the puzzle: they have identified mosquito antennae as receptors that allow insects to recognize lactic acid, a substance made of human sweat. Bugs are very attractive.

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The work started years ago when Dr. DeGennaro, who worked in Leslie Vosshall's laboratory at Rockefeller University, identified mosquitoes identified as having another odorant receptor to prey on. Even if this receptor was destroyed, mosquitoes could still find humans as long as carbon dioxide floated in the air. This suggested that other receptors, presumably detecting carbon dioxide, compensated for the loss.

Dr. DeGennaro and his colleagues went in search of these other players, starting with a receptor called Ir8a. Her role was not clear yet. The researchers placed mosquitoes without Ir8a in chambers where they were exposed to various combinations of carbon dioxide, lactic acid, warm temperatures and the arms of volunteers.

Keep track of what the mosquitoes have attracted among them Different conditions showed that the mutants had problems.

"We just did a simple behavioral test to see if they could respond to lactic acid," Dr. DeGennaro. "And they could not do that."

Lactic acid was identified decades ago as one of the key signals in human sweat for pulling mosquitoes. So far, however, it was not clear how the mosquitoes perceived it. The knowledge could eventually lead to defenses that hamper the normal functioning of Ir8a, or support the construction of effective traps, Dr. Gennaro.

Diseases such as Zika, West Nile, Dengue fever and malaria are spread by mosquitoes and getting numbers is an important global health goal. Dr. DeGennaro said that new effective mosquito repellent strategies that can be combined with each other are crucial. For example, the use of an insecticide alone promotes the development of resistant insects. With traps, chemicals that can kill larvae, and other tools used at the same time, this can have an impact.

However, the identity of the receptor or receptors that absorb carbon dioxide is still a mystery. Dr. DeGennaro and his colleagues believe that it can be in the same receptor group as Ir8a, but they have not found it yet. The search continues.

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