Some people seem to get eaten alive by mosquitoes each summer, while others sail through the season with nary a bite.
Certain mosquito species are attracted to, or repelled by, different subsets of people depending on the components of their body chemistry and skin microbiome, researchers report July 30 in iScience. Understanding how mosquitoes choose their hosts could help prevent the spread of mosquito-borne illnesses, including dengue, West Nile and yellow fever.
“We want to understand what people’s risks are for being bitten because all of these mosquitoes that we studied are vectors of disease,” says Matthew DeGennaro, a neurogeneticist at Florida International University in Miami. Manipulating the molecules and bacteria that influence attraction could help scientists create new kinds of commercial mosquito repellents, he says.
Mosquitoes locate their dinners through visual, thermal and scent cues. But human scent is the product of more than a thousand chemicals, many of which are produced by bacteria that live on our skin. That makes it challenging to know which specific cues mosquitoes rely on to find their preferred human hosts.
DeGennaro and colleagues recruited 119 volunteers and exposed three different species of mosquito to each person’s scent. For Aedes aegypti and Aedes albopictus, which feed during the day, volunteers placed an arm inside a device designed to let the mosquitoes smell them but not bite. To observe Culex quinquefasciatus, which feed at night, each volunteer wore a nylon sleeve for several hours to capture their scent, and the researchers placed the sleeve into the apparatus in the dark. For each person or sleeve, the scientists measured how many mosquitoes of each species entered the device to investigate.
Each mosquito species preferred a different group of volunteers, the team found. A. aegypti even showed a slight but meaningful preference for males over females. Though some people had more than one mosquito species find them particularly attractive, no one strongly attracted all three species.
The team also collected samples of the volatile compounds in the air around each person’s arm and of the bacteria living on their skin that may have created some of those compounds. Then the researchers looked for commonalities among the small groups of people who were most and least attractive to each mosquito species, respectively.
Ae. aegypti and C. quinquefasciatus tended to be more attracted to people who had less skin odor overall, the team found. Ae. albopictus was attracted to 13 chemicals with plantlike odors. Certain skin bacteria were present in all three high-attraction groups, including Corynebacterium kefirresdentii, Cutibacterium granulosum and a strain of Staphylococcus epidermis.
Because human odor is so complex, it’s difficult to detect all of the classes of compounds that comprise it, says Maria Elena De Obaldia, a research program manager at the drug developer Regeneron Pharmaceuticals in Tarrytown, N.Y., who was not involved in the work but previously studied mosquitoes’ attraction to humans. (Regeneron is a major financial supporter of the Society for Science, which publishes Science News.) It’s possible there are other compounds that influence attraction that weren’t captured in this study, she says.
Still, the different species’ preferences suggest that each species may have evolved its own way of finding hosts. Those adaptations may have been influenced by the types of host each species feeds on and the time of day that they seek out food, says Alicia Showering, who was not involved in the study. Showering is the CEO of BugBiome, a Norwich, England–based company that develops insecticides from microbes that live on crops.
The team now plans to study how skin bacteria produce odors that are more or less attractive to mosquitoes, says Kaylee Marrero, a mosquito neurobiologist at Florida International University in Miami. That may help researchers develop microbe-based repellants or lures for traps that target the most prevalent species in an area, she says.
“We’re all trying to figure out how to stop people from getting sick,” Marrero says. “Figuring out why [mosquitoes] are biting people is the best way to do that.”
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