Those who have spent a few days in nature during the summer may have noticed that mosquitoes seem to be more attracted to some individuals than others. However, the science behind why female mosquitoes prefer certain people for their blood meals remains partially unexplained.
To address this mystery, a team of researchers from Johns Hopkins University (USA) and the Macha Research Trust (Zambia) constructed a large flight cage. They aimed to expose mosquitoes to a variety of odors and analyze their behavior under natural conditions.
Previous experiments investigating mosquitoes’ olfactory preferences have been conducted in laboratories on a small scale, potentially yielding inaccurate results due to the lack of replication of natural conditions. In their study, published in Current Biology, the researchers overcome this limitation by building a semi-field flight cage in Zambia with a volume of around 1,000 cubic meters.
During the initial stage of the experiment, 200 hungry mosquitoes were released into the cage each night. The researchers monitored the frequency with which the mosquitoes landed on heated platforms impregnated with human odor or carbon dioxide, simulating conditions similar to human skin.
Following these observations, six volunteers slept in individual camps near the cage for six consecutive nights. Their scents were channeled to the heated platforms through air conditioning ducts. Nocturnal air samples were collected from the tents to analyze and compare the airborne components of each person’s odor.
Despite variations in odor each night, the researchers identified approximately 40 chemical substances that could attract mosquitoes. Individuals who were more attractive to mosquitoes emitted higher concentrations of carboxylic acids, likely produced by skin microbes.
Conversely, the person who was least appealing to mosquitoes emitted roughly triple the amount of eucalyptol, a compound found in many plants, compared to the others. It is suspected that this high concentration was due to their vegetarian diet.
The researchers plan to replicate the tests with 100 to 120 volunteers in order to further understand the olfactory signature that makes some humans attractive to mosquitoes and other blood-sucking insects. These findings could potentially contribute to the development of new repellents and the control of disease outbreaks transmitted by these insects.