People who are often bitten are not necessarily bitten by all mosquito species. A study conducted with 119 volunteers shows that each species favors different human profiles. This variation depends in particular on the odors emitted by the skin and the bacteria that live on it.
The researchers compared three mosquito species capable of transmitting diseases: Aedes aegypti, Aedes albopictus and Culex quinquefasciatus. The participants were tested in an olfactometer, a device that measures an insect's attraction to an odor source.
Illustration image from Pixabay
The three species did not choose the volunteers in the same order of preference. A person very attractive to one could therefore leave another species almost indifferent. This result contradicts the idea of a “mosquito magnet” that works in all situations.
To understand these preferences, the team analyzed the odorant molecules present on the skin. It also studied the skin microbiota, that is, all the micro-organisms naturally living on its surface. These bacteria contribute to the production or transformation of many body odors.
In Aedes aegypti and Culex quinquefasciatus, strong attraction was associated with the absence, rather than the presence, of certain odors. The researchers specifically mention cyclic alcohols and monoterpenes, a family of molecules also produced by many plants.
Aedes albopictus, often called the tiger mosquito, had a different profile. Its attraction was linked to the presence of certain ketones, organic compounds that can contribute to the odor of the skin. The study therefore shows that the same molecules do not act identically on each species.
A difference related to the sex of the volunteers also appeared for Aedes aegypti. This species was more attracted to men than to women under the test conditions. No comparable effect was observed for the other two species studied.
Human odor forms a mixture of many compounds, whose proportions vary between individuals. Mosquitoes also use other signals, such as exhaled carbon dioxide, heat and humidity.
These results could help design repellents or traps adapted to a specific species.