The deadliest animal on Earth would cause a lot less trouble if it preferred to feed on the blood of cattleinstead of the blood of humans.Many of the approximately 3,500 mosquito speciesactually do prefer cowsor pigs, dogs, or other animals. But it's thesmall number that don't that kill hundreds of thousands of people every year by spreading malaria, dengue, Zika, and other illnesses.Figuring out why the mosquitoes that spread those diseasesprefer humans helps us figure out how to control or kill thosepopulations. And it turns out that a large part of that preference is genetic, which for certain deadly species in particular might point towards new mosquito control strategies.For some mosquito species, like the Aedes aegypti that spread dengue and Zika, we've long known aboutthe genetic preference that drives them to seek out humans.Now, a new study published inPLOS Genetics reveals for the first time whycertain populations of one species ofAnopheles malaria-spreading mosquitoes prefer humans and other populations of the same mosquito prefer cattle. (AnophelesandAedes populations split about 150 million years ago, long before humans walked the Earth, meaning they most likely independently evolved the traits that unfortunately lead them both to want to feed on us.)In East Africa, the study explains, successful malaria control efforts have stopped much of the malaria transmission byAnopheles gambiae mosquitoes. They preferto feed on humans andrest indoors, and so long-lasting indoor insecticides have managed tosuccessfully wipe out many of them.That leavesAnopheles arabiensis as the main malaria vector in the region, and this sub-species is much more confusing. It seems to feed on animals and humans alike and to rest both indoors and outdoors, making it "more of a generalist," according to the study, which makes it harder to control.After collecting hundreds of specimens ofarabiensis mosquitoes that had fed from cattle and people from three Tanzanian villages, the researchers conducted whole genome sequences on 48 of the bugs.They were able to pin down certain genetic patterns that they thinkexplain why certain mosquitoes prefer humans and why others prefer cattle. They didn't find any genetic explanation for whether the bugs rested indoors or outdoors, and so they assume that these mosquitoes can adapt their napping behavior to wherever happens to be convenient. That adaptability makes it much harder to figure out how to vanqish them.Other research has shown that if you keep cattle near mosquitoes who prefer to feed on cattle but can spread malaria to humans, it can reduce disease transmission rates up to 50%. In other words, if you make a cow available, the mosquitoes will bitethe cow and leave the human alone.The scientists behind the work write that they'll need to confirm this finding based on a broader geographic sampling, but it could offer helpful strategies for the battle against malaria.First of all, if they develop tests that can identify the preference for human-biting mosquitoes, these could be used to target high-priority regions for mosquito eradication.Additionally, they suggest that it might be possible to genetically engineer more of these mosquitoes with a preference for feeding on cows, which could help spread this trait and hopefully reduce the frequency of the genes associated with a preference for human blood.SEE ALSO:Some people don't get bitten by mosquitoes 'why that's true may surprise youJoin the conversation about this storyNOW WATCH: Mosquitoes are the most dangerous creatures on Earth ' should we kill them all
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