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We all have around us a friend, family member or someone close to us who appears to be the target of choice every summer for mosquitoes. These people go through the summer season with suffering, enduring the assaults of these bloodthirsty flying creatures daily. On the other hand, it is very likely that you also know a person who seems to avoid bites in an almost magical way, as if mosquitoes could not approach or bite them.
How come these insects seem to develop a preference for some humans over others ? A team led by Dr. Conor McMeniman, assistant professor of molecular microbiology and immunology at the Johns Hopkins Bloomberg School of Public Health and the Institute of Malaria Research at Johns Hopkins in Baltimore examined this topic. The study, published in May 2023, was also carried out in collaboration with the Macha Research Trust in Zambia. The answer lies in one word: chemistry.
Mosquitoes prefer stinky cheese
Distant cousins of flies, mosquitoes draw their energy mainly from flower nectar. However, females, driven by the reproductive instinct, need an additional supply of protein to ensure the development of their eggs. And this is where human blood comes in, the favored delicacy of these insects. To spot it, these formidable, but tiny nocturnal huntersrely on a formidable weapon: their keen sense of smell.
The study was able to pinpoint the chemical substances present in body odors, irresistibly attracting mosquitoes. In order to uncover the secrets of mosquitoes' preference for certain humans over others, researchers have set up a large-scale testing arena. Imagine a vast structure the size of an ice rink, dotted with tents where participants slept peacefully. The air from these tents, infused with each sleeper's unique body odors, was then pumped to the main facility, where hundreds of hungry mosquitoes awaited their prey. Equipped with infrared cameras, the researchers observed the movements of the mosquitoes to see where they were heading.
The results were clear: some participants seemed irresistibly appetizing to the insects, while others aroused their indifference, or even their repulsion. So it's not a legend. Chemical analysis of the air made it possible to identify the culprit substance. Mosquitoes are attracted to carboxylic acids, compounds present in human sweat, but also… in very odorous cheeses. Limbourg, in particular, a soft German cheese, contains a good amount of butyric acid, which is part of the carboxylic acid family.
This is present on human skin, but it is completely imperceptible to our sense of smell. On the other hand, for mosquitoes, it acts as an irresistible olfactory signal telling them that a feast is near. Conversely, certain compounds, such as eucalyptol, an aromatic compound found in certain plants, appeared to act as a natural repellent. This discovery therefore suggests that the diet of humans, by modifying the smell of their sweat, could also influence their attractiveness to mosquitoes.< /p>
Implications for disease control
This study could radically change our approach to fighting certain diseases, particularly malaria, which decimates more than 600,000 people each year, mainly children under five and pregnant women. Thanks to a better understanding of the olfactory mechanisms that guide mosquitoes towards their prey, researchers hope to develop lures or repellents of a new kind. Devices which could, therefore, disrupt the host-seeking behavior of the female mosquito.
Dr. Edgar Simulundu, scientific director at Macha Research Trust and co-author of the study, s’was very enthusiastic about the possibilities offered by this discovery: “< em> This paves the way for the development of lures or repellents that can be used in traps to control malaria vectors in areas where the disease is endemic ”. An optimism shared by Dr. Leslie Vosshall, a neurobiologist at the Howard Hughes Medical Institute, who called the study “super exciting “.
Mosquitoes do not choose their victims at random and have an appetite for certain chemical compounds emitted by our bodies, this is now a certainty. This scientific contribution could therefore, ultimately, save millions of lives, particularly in the poorest regions of the world where malaria and other diseases transmitted by mosquitoes continue to wreak havoc. While this research will not save your future barbecue, it will provide valuable clues to guide our future strategies to combat these pests.
- A study looked at mosquitoes, specifically their propensity to bite some humans more than others.
- It revealed that these insects were olfactory guided and preferred organisms that released carboxylic acids.
- Thanks to the understanding of this mechanism, the fight against diseases transmitted by mosquitoes can be optimized .
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