Fatty acids on the skin explain why some people are “mosquito magnets”

2022-10-19

If you’re one of the unlucky ones that seems to get ravaged by mosquitoes while others around you escape unscathed, a new study offers an explanation as to why. Scientists have examined what makes mosquitoes more attracted to some humans over others, and uncovered a strong association between being a so-called mosquito magnet and elevated levels of fatty acids on the skin.

Mosquitos are known to track down their human victims through a range of sensory cues that include body heat, CO2 exhalation and body odor. Research in this area has produced some interesting insights of late, including a paper published earlier this year that showed how viruses can change the skin microbiome to alter the odor of person, luring in mosquitos to hitch a ride to their next host.

This new work from scientists at The Rockefeller University also focused on the skin and the way its odors may attract mosquitoes. The scientists tasked participants with wearing nylon sleeves on their forearms to capture the scent of their skin, with the sleeves then paired up and placed in tubes to face off in a round robin–style tournament of mosquito attractiveness.

This saw Aedes Aegypti mosquitoes, which are the primary vector for diseases like Zika and dengue, placed in a chamber with access to two tubes, each containing a nylon sleeve. Ultimately this enabled the scientists to profile the attractiveness of 64 human subjects to mosquitoes, which produced some compelling results.

The team found one target, which they’ve called Subject 33, was much more attractive to the mosquitoes than the others. This subject was four times more attractive to the mosquitoes than the next best, and 100 times more attractive than the subject at the bottom of the mosquitoes’ hit list. In any of the team’s experiments, the mosquitoes swarmed toward this sample.

“It would be obvious within a few seconds of starting the assay,” said study author Maria Elena De Obaldia. “It’s the type of thing that gets me really excited as a scientist. This is something real. This is not splitting hairs. This is a huge effect.”

Chemical analysis followed and revealed 50 molecular compounds that were heightened in the skin of the more attractive subjects. One type in particular was produced at much higher levels than less attractive subjects. Called carboxylic acids, these fatty substances help give the skin a distinct odor that appears to be much to the liking of blood-hungry mosquitoes.

“There’s a very, very strong association between having large quantities of these fatty acids on your skin and being a mosquito magnet,” said study author Leslie Vosshall.

And apparently being a mosquito magnet is not an easy tag to shake. Some of the participants in the research were studied over several years, and their body odor seemed to continue attracting mosquitoes, no matter what else about their behavior had changed.

In follow-up experiments, the scientists attempted to engineer mosquitos that couldn’t distinguish between attractive and less attractive humans in this way. This involved creating mutant mosquitoes missing key odor receptors, but the insects were still able to hunt down their favored victims.

“The goal was a mosquito that would lose all attraction to people, or a mosquito that had a weakened attraction to everybody and couldn’t discriminate Subject 19 from Subject 33. That would be tremendous,” Vosshall says, as it could lay the groundwork for new and improved mosquito repellents. “And yet that was not what we saw. It was frustrating.”

For now, it’s back to the drawing board, with the scientists now pondering the idea that manipulating the skin microbiome to alter its odor could create a mosquito-masking effect. They also hope the research leads to experiments on other mosquito species, such as Anopheles, which spreads malaria.

“I think it would be really, really cool to figure out if this is a universal effect,” said Vosshall.

The research was published in the journal Cell.

New Atlas, 19 October 2022
; https://newatlas.com