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Why do mosquitoes target humans?

, published on Sunday 02 August 2020 at 08h00

In the heart of summer, they are often synonymous with inconvenience. Tiger mosquitoes have been the subject of a new study, which shows that the appetite of sick aegpyti for human blood grows with the development of human activities.

It’s a summer ritornello.

Mosquito bites when going outdoors or in the middle of the night. A study published in the journal Current Biology looked at the attraction of tiger mosquitoes (Aeges Aegypti) for human skin. According to the document published on July 23, 2020, two environmental factors push these “pests” to target humans. The study carried out in 27 locations in sub-Saharan Africa suggests that the humidity level and the density of the population push mosquitoes to bite humans rather than animals.

The study thus shows the consequences of urbanization and global warming on mosquitoes’ appetite for human blood, which is only expected to increase over the years. “We wanted to better understand what prompts them to adapt to humans,” said Noah Rose, who led the study.

Mosquitoes thus target areas of water stored by human activity to ensure their survival, and thus target their closest potential victims for food. Galloping urbanization in several areas of Africa could thus lead to a sharp increase in bites of tiger mosquitoes by 2050, vectors of viruses such as yellow fever, dengue or Chikungunya.

No “sweet blood” theory, but a myriad of factors

In France, the tiger mosquito has proliferated over a large part of the territory. Its presence has thus been observed in 58 departments. As for the “choice” of its victims, several elements must be taken into account.

In an article published in 2013, the American Smithsonian Research Institute lists several factors, including blood type and human production of carbon dioxide. The mosquito detects its prey by CO2 emissions, which it can, according to The Smithsonian Institute, perceive up to 50 meters away. According to the same source, individuals exhaling more CO2 are thus more likely to be detected, which is why children are bitten less on average than adults.

The most exposed people are those with a higher metabolism, including people of larger build as well as pregnant women.

In 2011, the professor of entomology Jonathan Bay, explained that 20% of the population had characteristics that are highly attractive to mosquitoes. In addition to the “smell” of CO2, the latter respond, according to the researcher, to their sight. The “people dressed in dark colors (black, navy blue, red) stand out”, he explained for NBC News.

These elements, however, are only the first leads in a sea of ​​potential explanations. “With more than 350 components isolated from the odors produced by human skin, researchers have barely scratched the surface when it comes to mosquito preferences for some people,” said Joseph Conlon of the American Mosquito Control Association.

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