Zoe Sottile, CNN Posted Saturday, October 22, 2022 11:18 PM EDT Last Updated Saturday, October 22, 2022 11:18 PM EDT
(CNN) — If you’ve always suspected you might just be a mosquito magnet, scientists now have proof for you: Mosquitoes are, in fact, attracted to certain humans more than others, according to a new study.
A research team led by Leslie Vosshall, a professor at Rockefeller University and head of its neurogenetics and behavior laboratory, tried to identify why some people seem to draw more mosquitoes than others. The research results were published in the journal Cell on October 18.
Over the course of three years, researchers asked a group of 64 volunteers to wear nylon stockings on their arms for six hours a day over several days. Maria Elena De Obaldia, the study’s first author and a former postdoctoral fellow at Rockefeller University, constructed a “two-choice olfactometer assay”—an acrylic glass chamber into which the researchers placed two of the stockings. The study team then released yellow fever mosquitoes, scientifically called Aedes aegypti, into the chamber and observed which stocking attracted the most insects.
This test allowed the researchers to separate the study participants into “mosquito magnets,” whose averages attracted many mosquitoes, and “low attractors,” who didn’t seem as attractive to the insects. The scientists examined the skin of the mosquito magnets and found 50 molecular compounds that were higher in these participants than in the others.
“We had no preconceived notions about what we would find,” Vosshall, who is also chief scientific officer of the Howard Hughes Medical Institute, told CNN. But one difference was particularly distinctive: the mosquito magnets had much higher rates of carboxylic acid in their skin than the low attractants.
Carboxylic acids are found in sebum, the fatty substance that creates a barrier and helps keep our skin hydrated.
Carboxylic acids are large molecules, Vosshall explained. “They don’t stink that much by themselves,” he said. But beneficial skin bacteria “chew up these acids, which produce the characteristic smell of humans,” which may be what attracts mosquitoes, Vosshall said.
The smell of skin secretions plays a role
One participant, identified only as subject 33, was the belle of the ball for mosquitoes: the subject’s stockings were 100 times more attractive to mosquitoes than the less attractive participants.
And the level of attraction to humans appeared to remain fairly constant over time for participants who were monitored over the three-year period, Vosshall said.
Subject 33, for example, “never took a day off from being the most attractive human being,” which might be “bad news for mosquito magnets.”
When it comes to Aedes aegypti, female mosquitoes prefer to use human blood to fuel egg production, giving urgency to their search for humans to prey on. And these mini predators use a variety of mechanisms to identify and choose the humans they bite, Vosshall said.
Carboxylic acids are just one piece of the puzzle to explain how pesky insects can choose their targets. Body heat and the carbon dioxide we release when we breathe also attract mosquitoes to humans.
Scientists still don’t know why carboxylic acids seem to attract mosquitoes so strongly, Vosshall said. But the next step could be to explore the effects of reducing carboxylic acids on the skin.
“You can’t completely remove the skin’s natural moisturizers, that would be bad for the skin’s health,” he said. However, Vosshall said that dermatological products might be able to minimize carboxylic acid levels and reduce mosquito bites.
“Every bite from these mosquitoes puts people at risk for public health,” he said. “Aedes aegypti mosquitoes are vectors of dengue, yellow fever and Zika. Those people who are magnets will be much more likely to get infected with viruses.”
Mosquitoes evolved to hunt by scent
Matthew DeGennaro, an associate professor at Florida International University who specializes in mosquito neurogenetics, told CNN that the study’s results help answer long-standing questions about what specific factors make mosquitoes love some humans more than others. others He did not participate in the study.
“This study clearly shows that these acids are important,” he said. “Now, how mosquitoes perceive these carboxylic acids is interesting because these particular chemicals are very heavy, so they are difficult to smell from a distance.
“It could be that these chemicals are being disrupted by, let’s say, the skin microbiome, and it’s causing a certain type of odor plume. Or it could be that other factors in the environment are breaking down these chemicals a little bit , so they are easier for mosquitoes to detect.”
The results are also “a really cool example of how insects can smell,” DeGennaro added. “This insect has evolved to hunt us.”
For DeGennaro, the staying power of certain humans’ attractiveness is one of the most interesting aspects of the research.
“We didn’t know that there were very stable preferences of mosquitoes for certain people,” he said. “It might suggest that the skin microbiome is important, although they didn’t address that.”
Further research should explore the microbiome that lives on human skin to understand why mosquitoes are attracted to certain compounds over others, he said. And that could lead to better products to reduce mosquito bites and the spread of disease.
“I think if we understand why mosquitoes find a host, we can design new repellents that will stop mosquitoes from detecting these chemicals,” DeGennaro said. “And this could be used to improve our current repellents.”