DNA may be to blame for insect magnetism
New research shows that if mosquitoes are attracted to the scent of a particular person, they are likely to be attracted to a twin’s scent as well. On the flip side, if they are repelled by someone’s odor, they’re likely to find a twin repellent too.
Scientists tested 37 sets of twins willing to place their hands in a Y-shaped glass tube. Groups of 20 mosquitoes were released into the tube and given 30 seconds to assess the scents inside.
Then a gate was opened, allowing them to fly toward the hands they preferred and away from those they disliked. (Although the mosquitoes could smell the volunteers’ hands, they couldn’t reach them.)
Researchers found that the overlap in mosquito preference was about twice as high for identical twins (who share virtually all their DNA) as it was for fraternal twins (who share only half ).
That allowed them to calculate that 62 percent to 83 percent of a person’s degree of mosquito attractiveness is determined by DNA, according to a study published last month in the journal PLOS One.
To put that into perspective, other studies have found that genes are about 80 percent responsible for a person’s height and 50 percent to 80 percent for a person’s IQ.
Scientists have suspected for some time that those who find themselves playing the role of pincushion at barbecues and other outdoor gatherings have an unfortunate genetic inheritance.
They knew that biology played a role in either attracting or repelling mosquitoes. For instance, pregnant women are a much bigger draw than women who aren’t. They also know that people who are infected with the malaria parasite are more attractive to mosquitoes during the window when the infection can be spread.
Previous studies have shown that mosquitoes are drawn to people (or not) on the basis of their odor. Bacteria that live on skin play a role in producing body odor, but skin cells probably play a role too. If so, that might be controlled by genes.
So the researchers recruited 18 pairs of identical twins and 19 pairs of fraternal twins. All of them were women (so that the gender of the volunteers wouldn’t skew the trial results) and all of them were post-menopausal (so that changes in their menstrual cycle wouldn’t be a factor).
In some tests, the researchers compared the odor of one twin’s hand against clean air. In others, they tested twin versus twin. In others, both ends of the Y-shaped tube were pumped with clean air.
The new results leave no doubt that some people are genetically programmed to be attractive to mosquitoes, and others have DNA that functions as a natural mosquito repellent.
The researchers hope to use this knowledge to trick mosquitoes into thinking that everyone is in that second category.
“We could possibly ... cause your body to produce natural repellents and would minimize the need to actually put repellents on your skin,” said James Logan, a medical entomologist at the London School of Hygiene and Tropical Medicine and one of the study’s senior authors.