Fatty acids emanating from your skin can make you a magnet to mosquitos, according to researchers.
In the three-year study, eight participants were asked to wear nylon stockings over their forearms for six hours a day. They repeated this process on multiple days. Over the next few years, the researchers tested the nylons against each other in all possible pairings through a round-robin style “tournament.” They used a two-choice olfactometer assay that De Obaldia built, consisting of a plexiglass chamber divided into two tubes, each ending in a box that held a stocking. They placed Aedes Aegypti mosquitoes—the primary vector species for Zika, dengue, yellow fever, and chikungunya—in the main chamber and observed as the insects flew down the tubes towards one nylon or the other.
Some People Are Mosquito Magnet
By far the most compelling target for Aedes aegypti was Subject 33, who was four times more attractive to the mosquitoes than the next most-attractive study participant, and an astonishing 100 times more appealing than the least attractive, Subject 19.
The samples in the trials were de-identified, so the experimenters didn’t know which participant had worn which nylon. Still, they would notice that something unusual was afoot in any trial involving Subject 33, because insects would swarm towards that sample.
The researchers sorted the participants into high and low attractors, and then asked what differentiated them. They used chemical analysis techniques to identify 50 molecular compounds that were elevated in the sebum (a moisturizing barrier on the skin) of the high-attracting participants. From there, they discovered that mosquito magnets produced carboxylic acids at much higher levels than the less-attractive volunteers. These substances are in the sebum and are used by bacteria on our skin to produce our unique human body odor.
To confirm their findings, Vosshall’s team enrolled another 56 people for a validation study. Once again, Subject 33 was the most alluring, and stayed so over time.
Can We Ever Escape Mosquitos?
Humans produce mainly two classes of odors that mosquitoes detect with two different sets of odor receptors: Orco and IR receptors. To see if they could engineer mosquitoes unable to spot humans, the researchers created mutants that were missing one or both of the receptors. Orco mutants remained attracted to humans and able to distinguish between mosquito magnets and low attractors, while IR mutants lost their attraction to humans to a varying degree, but still retained the ability to find us.
These were not the results the scientists were hoping for. Their goal was a mosquito that would lose all attraction or have weakened attraction to people. According to the researchers, Aedes aegypti has an exquisitely complex olfactory system. It’s a failsafe that the female mosquito relies on to live and reproduce. Without blood, she can’t do either. Aedes aegy has “a backup plan and a backup plan and a backup plan” and is tuned to these differences in the skin chemistry of the people it goes after.
The apparent unbreakability of the mosquito scent tracker makes it difficult to envision a future where we’re not the number-one meal on the menu. But one potential avenue is to manipulate our skin microbiomes. It is possible that slathering the skin of a high-appeal person like Subject 33 with sebum and skin bacteria from the skin of a low-appeal person like Subject 19 could provide a mosquito-masking effect.
For now, we will have to put up with mosquito bites. Possibly in the future, research like this may help produce a method that can reduce our delicious smell to mosquitos.
Source: Differential mosquito attraction to humans is associated with skin-derived carboxylic acid levels
This article is based on the press release The Rockefeller University. Content may be edited.