Some people can stand outside on a summer evening and walk back in without a single bite. Others get absolutely devoured. It turns out this isn’t bad luck or imagination. Mosquitoes appear to be responding to different chemical and microbial cues on each person’s skin. A new study tested 119 people against three different disease-carrying mosquito species, Aedes aegypti, Aedes albopictus, and Culex quinquefasciatus, and found something that could reshape how scientists think about mosquito repellents: each species ranked participants differently in the lab, so the person who acts as a magnet for one type may barely register with another.
For years, researchers have known that body odor plays a role in mosquito attraction. Most previous work, though, focused on a single mosquito species at a time, leaving a big question unanswered: do all mosquitoes prefer the same people? According to the research, published in the journal iScience, the answer is mostly no. Different species ranked the same group of people in very different orders of preference, meaning a person who is highly attractive to one species is not necessarily on the menu for another. Among the 119 participants, no one was a top target for all three species, and no one was at the bottom of the list for all three either.
One sex-based difference also stood out. One of the three species, Aedes aegypti, the mosquito that spreads dengue, Zika, and yellow fever, showed a slight but statistically significant preference for male participants over female ones, a pattern the other two species did not share.
Who Was Tested and How
Researchers at Florida International University, in collaboration with scientists at the University of Zürich, recruited 119 volunteers from Miami, Florida, aged 18 to 59. Participants were racially and ethnically diverse, and the group was split nearly evenly by sex, with 61 males and 58 females. To keep the results clean, participants were told not to shower the night before their visit and to skip deodorants, perfumes, or scented skin products.
Each volunteer stuck their left forearm into a specially built device, essentially a sealed tube that allowed mosquitoes to respond to a person’s natural scent without any physical contact. For two of the mosquito species, live arms were used. For the third species, Culex quinquefasciatus, a night-biting mosquito that also transmits West Nile virus, participants wore a thin nylon sleeve over their arms for 12 to 16 hours to capture their scent, since those mosquitoes were tested separately under low-light conditions that mimic nighttime.
Three species were tested in total: Aedes aegypti, which primarily targets humans and spreads dengue and Zika; Aedes albopictus, a related species with a broader diet that spreads similar viruses; and Culex quinquefasciatus, the night-biting species associated with West Nile virus. Across all 119 participants, Aedes aegypti showed the highest average attraction rate at about 89%, Culex quinquefasciatus came in around 43%, and Aedes albopictus had the lowest average at about 27%. These differences in overall enthusiasm for humans may reflect how deeply each species has evolved to rely on human blood, though the study’s design does not directly establish that connection.
What Mosquitoes Are Actually Smelling
To figure out what made certain people more or less attractive, the research team collected the invisible cloud of chemicals coming off each participant’s arm and analyzed it to identify individual compounds. At the same time, they swabbed participants’ forearms to study the bacteria on their skin, cataloging 246 distinct bacterial taxa across the 119 participants.
Only one of those taxa appeared in every participant, a notable result given how much the skin’s microbial makeup varies from person to person. That variability, the researchers argue, is a key part of why mosquitoes respond so differently to different people.
For Aedes aegypti, the dengue-and Zika-spreading species, high attraction was closely linked to Staphylococcus bacteria on the skin, a pattern specific to this species and consistent with earlier research. People who were least attractive to this species tended to have more Pseudomonas bacteria on their arms, a pattern previously associated with reduced mosquito attraction. When it came to airborne chemicals, high attraction for this species was tied to the absence of certain compounds rather than the presence of appealing ones, hinting that these mosquitoes may home in on people who simply lack natural deterrents.
For Aedes albopictus, the broader-diet species, the pattern flipped. High attraction was linked to the presence of specific appealing chemicals, including one compound previously tied to how mosquitoes evolved a preference for humans in the first place. Researchers found 13 volatiles were more common among people who scored highly on attraction to this species, compared with just one such chemical for Aedes aegypti. That broader set of appealing odors aligns with this mosquito’s more opportunistic nature, since it feeds on a wider range of animals rather than specializing on humans.
For Culex quinquefasciatus, the night-biting, West Nile-associated species, high attraction was again tied more to the absence of certain compounds than to the presence of appealing ones. No bacterial species were significantly linked to high attraction here, though bacteria in the Actinomyces group were associated with low attraction.
Source : https://studyfinds.com/why-some-people-attract-more-mosquitoes-than-others/