Mosquitoes: why do some people bite more than others? – Sciences

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Alcohol, blood sugar, blood type … mosquitoes always seem to hit the same people and you always find someone who thinks they know why. What is it that some of us are more frequent points? Several explanations have been provided by the scientists.

The summer and rising temperatures are accompanied, as every year, by the return of mosquitoes. Some of us may have the unpleasant feeling of always being targeted by these insects, while others seem to be spared. How do mosquitoes find us? And why do they seem to sting some people more than others?

Although these insects have small brains, their detection system is surprisingly sophisticated. Several studies have examined why mosquitoes bite us. Not surprisingly, blood is one of these. In 2004, a group of scientists noted in the journal Journal of Medical Entomology that the tiger mosquito seems to land more on the skin than people belonging to the blood group O, than on the skin of other people. They deduce that these individuals attract this species of mosquitoes the most. But is the composition of our blood the only explanation for this disparity?

Blood does not explain everything: we also refuse CO2

No, blood does not seem to be the only factor that explains the preference of mosquitoes. " Humans send hundreds of odorous molecules into the air Insects use to find us, the neuroscientist Helen Shen explained in the diary PNAS in 2017. Mosquito-activated neural networks are poorly understood, since the signals they use appear to be different. In the years 50 and 60, carbon dioxide, heat or humidity have been identified as elements that help mosquitoes find us.

In 2013, a review of the magazine cell confirmed that some mosquitoes had a receptor that allowed them to detect carbon dioxide that we are running out. This same neuron would also be involved in detecting our body odor. The study included the mosquitoes Aedes aegypti (the main vector of dengue) and Anopheles gambiae (vector of malaria).

The role played by carbon dioxide, as a signal used by mosquitoes to find us, would explain why pregnant women tend to attract more mosquitoes. Several studies have examined the question. In 2000, scientists find in the diary The Lancet Pregnant women seemed to attract more mosquitoes than the Anopheles gambiae than other women who were not pregnant. Scientists therefore hypothesized that " physiological and behavioral changes that occur during pregnancy It could affect the attractiveness these people can cause in mosquitoes.

Pregnant women can attract more species of mosquitoes. // Source: Pexels (cropped photo)

Pregnant women release more carbon dioxide and moisture into their breath. Their body temperature would be slightly higher, which releases more volatile substances onto the surface of their skin, helping mosquitoes locate them. Another study, published 3 years later in the journal Annals of tropical medicine and parasitologyalso finds that pregnant women are bitten by Anopheles arabiensis (a species of anopheles gambiae), compared to other women who do not expect a baby.

Sweat, clothes, alcohol: do they play a role?

Our body odor, our heat, our humidity … mosquitoes could also identify acidic substances in our sweat. A particular olfactory receptor seems to be involved in the ability of these insects to identify us, the scientists showed in a study published in the journal Current biology in March 2019. They deprived the Aedes aegypti mosquitoes of this receptor and discovered that the insects appeared less attracted from human odors.

Another explanation would be related to the color of the clothes we wear. second Jonathan Day, an entomologist of the University of Florida, mosquitoes do not only use odors to identify their prey: vision also plays an important role. He explained to our colleagues NBC news when wearing dark colors, such as black, blue or red, mosquitoes could be more easily spotted when we move.

Dark clothes would help mosquitoes find us. // Source: Pexels (cropped photo)

Can we swallow the attraction we have for mosquitoes? A study published in 2002 in the journal Official of the American Mosquito Control Association establishes a possible link between alcohol consumption and mosquito attraction. These lands are more frequent on study volunteers, after having consumed beer (350 milliliters). However, this study was conducted on a panel of 13 people, so you need to draw your conclusions very carefully.

A link with the diversity of bacteria on our skin

Another explanation, which seems already more plausible, was presented in 2011 in the magazine PLOS One. Scientists highlight a link between the tendency of mosquitoes to bite us and the community of bacteria present on our skin. This could play an important role in helping the mosquito find us. This element seems to be one of the most important variables explain why people are more pungent than others. The bacteria that populate our epidermis transform our secretions into volatile compounds. These compounds can contain up to 300 different elements: they are not the same for all individuals.

The communities of bacteria on our skin could attract more mosquitoes. // Source: Pexels (cropped photo)

Scientists observe that in the mosquitoes Anopheles gambiae, these bacteria have a role in detecting them. " The microbial communities on the skin play a key role in the production of the human odor. (…) The composition of the skin microbiota influences the attractiveness of humans for these mosquito species ", Details the authors. The individuals that seem" preferred "by this family of mosquitoes are those that have the least diversity of bacteria on their skin (compared to people who are more points). There is therefore a correlation between the bacterial genera and the degree of attractiveness of mosquitoes.

If you feel more like your neighbor or your neighbor, you may not have the same bacteria as this person on your skin. If this explanation is really the reason that explains these inequalities, the bad news is that it seems difficult to do something to fight it.

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