WHY do mosquitoes prefer to bite some people more than others? The answer to this irritating question may finally be on the horizon, at least for people infected with malaria.
Researchers have discovered that malarial parasites actually make their human hosts smell more attractive to mosquitoes when the parasites are ready to be transmitted, although it鈥檚 not yet clear how they do it.
鈥淭he malarial parasite manipulates the transmission from within,鈥� says Jacob Koella from the University of Pierre and Marie Curie in Paris, who carried out the study in Kenya.
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Koella placed three tents around a chamber of uninfected mosquitoes. In one tent he placed a child with transmissible malaria, in the next a child in the non-transmittable stage, and in the third a child without malaria. He then wafted the odour from the three children towards to the mosquitoes using a fan. After repeating the experiment with 12 sets of children, he concluded that twice as many mosquitoes targeted the child in the transmissible stage than each of the other two.
The experiment was repeated with the same children after they had been treated with anti-malarial drugs to kill the parasite. Those who had previously been more popular now seemed to be repelling the insects.
鈥淭he attractiveness was coming from the parasite, and not something intrinsic to the children,鈥� says Koella.
Malarial parasites have already been shown to manipulate the behaviour of their mosquito hosts, encouraging them to bite more when they are mature enough to survive in vertebrate bloodstreams, but this is the first time they have been shown to manipulate humans.
鈥淲hat鈥檚 surprising is that this is not to the advantage of anybody but the parasite,鈥� says Jo Lines of the London School of Hygiene and Tropical Medicine.
快猫短视频s now need to discover what is causing the change in odour, before the discovery can be exploited in any practical way.
