Sweat and blood: why mosquitoes pick and choose between humans
For some people, a mosquito in the room is a threat to any little patch of exposed skin, while others seem to go unscathed. Now scientists have discovered chemicals in human sweat that make certain individuals more attractive to the insects.
Those targeted most aggressively are likely to have higher concentrations of the chemicals in their perspiration, or simply sweat more, the US researchers say.
“Mosquitoes find us through their sense of smell, but until now we’ve known very little about how they do this,” said Professor John Carlson, a molecular biologist at Yale University.
Professor Carlson’s team found that a large part of the mosquito’s sense of smell, or olfactory system, is devoted to sniffing out human targets. Of 72 types of odour receptor on its antennae, at least 27 are tuned to detect chemicals found in perspiration. Identifying which receptors they use to navigate their way towards us could help to develop new ways of repelling, confusing and trapping the insects.
Malaria, which is carried by mosquitoes, affects up to 500 million people across the world’s tropical regions, and kills up to 3 million a year — the majority young children in sub-Saharan Africa.
“The world desperately needs new ways of controlling mosquitoes, ways that are effective, inexpensive, and environmentally friendly,” Professor Carlson said. “Some of these receptors could be excellent targets for controlling mosquito behaviour.” The study, published today in the journal Nature, focused on a malaria-carrying mosquito, Anopheles gambiae, common in sub-Saharan Africa.
The team tested the response of each of the mosquito’s 72 receptors to more than 100 different odours — some corresponding to fruity scents, others to more aromatic or musty notes. To ensure that each odour receptor was tested in isolation, the team carried out the experiment using mutant fruit flies that had been genetically engineered to carry mosquito odour receptors.
Having identified which biological scents generate the strongest response, and which receptors are involved, the team are now looking into whether other scents can be used to disguise the smell of a person from mosquitoes. “We’re now screening for compounds that jam these receptors and could impair the ability of mosquitoes to find us,” said Allison Carey, a PhD student at Yale who carried out the experimental work.
Malaria kills its victims by damaging red blood cells and clogging capillaries that feed the brain and other organs. In a second study, also published today in Nature, scientists identified a protein made by the malaria parasite that is essential for it to take over human blood cells. In the test tube, parasites in which the protein, plasmepsin V, was disabled were unable to secrete the proteins that allow them to commandeer blood cells. The findings open the possibility of using drugs to block the action of plasmepsin V.
“The world desperately needs new ways of controlling mosquitoes, ways that are effective, inexpensive, and environmentally friendly,” Professor Carlson said. “Some of these receptors could be excellent targets for controlling mosquito behaviour.” The study, published today in the journal Nature, focused on a malaria-carrying mosquito, Anopheles gambiae, common in sub-Saharan Africa.
The team tested the response of each of the mosquito’s 72 receptors to more than 100 different odours — some corresponding to fruity scents, others to more aromatic or musty notes. To ensure that each odour receptor was tested in isolation, the team carried out the experiment using mutant fruit flies that had been genetically engineered to carry mosquito odour receptors.
Having identified which biological scents generate the strongest response, and which receptors are involved, the team are now looking into whether other scents can be used to disguise the smell of a person from mosquitoes. “We’re now screening for compounds that jam these receptors and could impair the ability of mosquitoes to find us,” said Allison Carey, a PhD student at Yale who carried out the experimental work.
Malaria kills its victims by damaging red blood cells and clogging capillaries that feed the brain and other organs. In a second study, also published today in Nature, scientists identified a protein made by the malaria parasite that is essential for it to take over human blood cells. In the test tube, parasites in which the protein, plasmepsin V, was disabled were unable to secrete the proteins that allow them to commandeer blood cells. The findings open the possibility of using drugs to block the action of plasmepsin V.
source - Times Online.com