Exactly how do mosquitoes zero in on humans to feed on? Scientists have figured out the guilty olfactory receptor and are working on a way to create a life-saving "perfume" that can protect people from mosquito bites.
When looking for a bloody meal, mosquitoes first sense the carbon dioxide a human exhales even from a distance of over 30 feet. Following this trail, the mosquito soon senses the human scent and, not long after, detects the human’s body heat. Once they land, they can taste the human skin with their legs and find a place to bite.
For years, it has been known that it is the lactic acid and other acidic volatiles in human sweat that attracts mosquitoes. For four decades, researchers have been trying to find out exactly how mosquitoes zone in on these scents, and now, using genetics, researchers have found the olfactory receptor that is responsible: Ionotropic Receptor 8a, or IR8a.
Biologist Matthew DeGennaro and his research team experimented with different mutant mosquitoes, and found that it is the absence of IR8a that made the mutant mosquitoes struggle to detect lactic acid and the other acidic components of human odor. While they are still able to detect carbon dioxide and heat, the missing IR8a made over half of the mutant mosquitoes uninterested in eating.
In the first test, Ph.D. student Joshua Raji experimented with his own arm. When he exposed his arm to wild mosquitoes, his scent was quite popular. But in four minutes of exposure to the mutant mosquitoes, not one took an interest in his arm. When they conducted the same test on 14 participants, the results were the same in that the genetically altered mosquitoes were significantly less likely to fly close to human skin.
There are many possible ways to use this information to prevent mosquito bites and thereby reduce the burden of mosquito-borne diseases. One of these ways is by using odors that mask the IR8a pathways. By adding such odors to repellents such as DEET, the repellents’ effectiveness may be increased.
So far, the team is working on chemical screens that disrupt the IR8a pathways, with the ultimate goal of making a “perfume” that masks people’s odors to mosquitoes, thereby protecting them from mosquito bites.
The study is published in Current Biology.