There are two main reasons mosquitos are attracted to humans. One is color (blues and blacks are bad dress choices on summer evenings). The other is smell. We emit signature chemicals that make us targets.
Mosquitos don't actually know we're humans, though. They just think they know from the limited way they see and smell. And so, for this reason, it may be possible to trick them into going after other targets, if those targets seem human. If you could make other animals smell like people, you might be able to draw them away, and thus reduce the damage mosquitos do all over the world.
That's a tactic being pursued by ISCA Technologies in California. It's developed a scent to spray on animals, so mosquitoes pick on cows instead of seeking out human flesh. "We saw there was a way of manipulating the mosquitoes by changing the odor profile of these animals," explains president Agenor Mafra-Neto. "Now we can attract mosquitoes that otherwise would be transmitting diseases to humans and bring them to animals nearby."
Now, you might think that would be unfair on cows. But Mafra-Neto says killing mosquitos that come into contact with animals is easier than those troubling humans. You can spray them with insecticide, for one, or perhaps simply deworm them. Research shows that well-known anti-worm treatments like Ivermectin could have a secondary role as insect killers. Once mosquitos take a bite of a recently dosed animal, they die quickly.
ISCA recently picked up a $100,000 grant from the Bill & Melinda Gates Foundation to trial its "cologne" in the U.S., Brazil, and Kenya. Mafra-Neto hopes the chemical—which can be formulated into a cream or shampoo—will be used at the same time as mass de-worming campaigns. That way, the mosquitoes can be drawn to the animals, then summarily executed.
"We can immediately kill the mosquitoes and stop the cycle of the disease that goes from mosquito to human and then back to humans," he says.
The scent—which lasts between two and four months—contains lactic acid, one the chemicals humans emit that animals don't. In concentrated form, ISCA's formulation smells a little like chicken soup, Mafra-Neto says, though not in an unpleasant way.
Potentially the baiting tactic could be a cheap way of saving lives, though it's still too early to say whether it will be as effective in the field as it appears in the lab. Mafra-Neto expects the research to continue for another year or so, at which point he'll decide whether to bring a full product to market.