Mosquitoes do not bite us at random: here are their selection criteria according to a new study

A new American study on mosquitoes presented by the American University John Hopkins has shown that these insects do not choose their prey at random. They would be equipped with sensors specific to a specific function, such as their attraction to the colors black, red or navy blue.

Having sweet blood, turning off the light, spraying yourself with lemongrass… There are many misconceptions about mosquitoes. One thing is certain: these insects feed on the proteins contained in our blood. But having sweeter blood would in no way be the cause of their bites.

“A receiver for every smell”

A new study published by scientists from Johns Hopkins University in Maryland has shown that mosquitoes do not bite randomly. They would select their prey according to several factors and thanks to sensors. In a press release of February 21, 2023American scientists claimed that they had spotted receptors that would allow them to choose their prey.

Located at the level of their antennae on nerve cells, these sensors would even make it possible to make the difference between the species: “Mosquitoes are sensitive to a lot of smells. This is not done like in our country, it is targeted because a receiver picks up one smell and not another. To sum up, there is a receiver for each smell”explains Jean-Baptiste Ferré, entomologist at the Interdepartmental Agreement for Mosquito Control of the Mediterranean Coast (EID) in Montpellier.

Odor, taste and ionotropic receptors

And to identify these new sensors, scientists from the American university used the technique of fluorescent in situ hybridization (FISH in English), which makes it possible to locate messenger RNA by fluorescent marking on the genes. Using this method, they were able to find 3 kinds of receptors in the complex olfactory system of mosquitoes.

Odor receptors, allowing insects to differentiate between humans and animals. The taste receptors that capture up to 50 meters, the carbon dioxide that we emit. A pregnant woman or a sick person has a higher metabolism, emits more CO2 and will be much more likely to be bitten according to Jean-Baptiste Ferré. He specifies : “Mosquitoes are attracted by the CO2 emitted by humans. But once excited by this CO2, they activate another receptor which will look for odors on our body such as body odors or even bacteria on our skin.”

This second sensor therefore depends on the first. Called ionotropic receptor, it is one of the most important in mosquitoes, especially in Aedes aegypti. It captures acids and aminos from the skin. According a study published on the Florida International University website, deletion or disruption of this receptor would reduce the mosquito’s host searches by 50%. Good news to prevent mosquito bites or even diseases.

A penchant for blood types A and O

John Hopkins’ study also evokes the preference of these insects for blood groups A and O rather than B. Jean-Baptiste Ferré does not explain it but mentions a possibility: “They don’t explain it yet, but we know that blood groups affect the composition of our blood and in particular our platelets. For example, people with group O have a little more fluid blood and therefore easier to pump. for the mosquito.”

He adds that these are trends and that there is no typical profile for these pests: “What I find interesting in the study is that there is not a single factor but many elements that combine. There are no people who are less stung but rather people who are less sensitive to those bites.”

How to avoid the bites of these pests?

For the Montpellier entomologist there is no miracle solution: “What works are skin repellents that must be repeated several times. To date, there are only 4 recognized and approved repellent molecules. Or you can put fans to keep mosquitoes away, because they don’t fly very well.”

But a problem has appeared in Montpellier recently. The EID has noticed that several species of mosquitoes coming from the marshes are now moving to the outskirts of the city: “In particular tiger mosquitoes, which are attracted to stagnant water”says Jean-Baptiste Ferré.

And for the future nothing is less certain. Episodes of severe drought are often followed by stormy episodes: “And it helps hatch the eggs of tiger mosquitoes in cities and swampy areas.” According to the EID expert, if climate change becomes more severe, summers will be hotter and therefore less conducive to the development of mosquitoes, but “on the other hand, we will undoubtedly have mild springs and winters, which will allow mosquitoes to proliferate much more”.

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