HomeScienceThe mosquito-attracting molecule discovered

The mosquito-attracting molecule discovered

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Substance discovered that produces the odor that makes mosquitoes bite more on certain people

In every family there is a member for whom mosquitoes seem to have a special predilection. Popularly, it was said that the reason why with the arrival of the summer nights some wake up full of bites and others practically intact is because the first ones have ‘sweet blood’.

And, in fact, it seems that the reality may not be too far from this theory. A study published in the scientific journal Cell has found not only that mosquitoes are attracted to certain odors, but that some viruses transmitted by these hematophagous insects change the way we smell, attracting them to perpetuate the pathogen cycle.

Diseases that attract mosquitoes

The idea that diseases transmitted by animal vectors (zoonoses) make you more attractive to that vector is not entirely new. Quite the contrary, it had already been convincingly demonstrated to be the case for malaria. A 2018 investigation concluded that people infected with the parasite that causes this disease tended to receive more mosquito bites than those who were not infected.

However, mosquitoes carry more diseases than malaria. For example, flaviviruses, such as those that cause dengue or Zika, cause tens of millions of infections annually through mosquito bites. And until now it had not been possible to show that they change our attractiveness to mosquitoes as we knew malaria does.

Now the authors of the paper cited above, from China, have found not only that these viruses change people’s smell, but also exactly how they do it.

Live demonstration

To demonstrate this, the scientists took three connected boxes and placed mosquitoes in the middle one, healthy mice in one of the others, and Zika-infected mice in the other. Adjusting for various factors, such as body temperature (by providing a fever-provoking drug, as occurs in Zika infection), they observed that the mosquitoes did not move equally toward the two boxes with mice.

More specifically, up to 70% of the mosquitoes went to the box of the Zika mice, and only 30% to the box of the healthy mice, demonstrating a clear preference.

This is supported by the fact that, when an odor filter was placed between the mice and the mosquitoes, the latter stopped showing any preference and moved in equal proportion to the two adjacent boxes.

Acetophenone, a key substance

The authors go even further, and to determine which chemicals specifically the mosquitoes preferred, they took a mass spectrometer and identified the chemicals emitted by both groups of rodents.

They then exposed the mosquitoes to each of these chemicals to see which ones made the mosquitoes move their antennae more (which is a sign that an odor is appealing to them). Using this method, they found that their favorite, acetophenone, was ten times more present in the odor of infected mosquitoes than in healthy ones.

Even by analyzing skin bacteria, they found the method by which Zika virus infection makes mice smell more attractive to mosquitoes (it inhibits the formation of an antibacterial molecule in their bodies, which causes other bacteria that produce acetophenone to proliferate.

An avenue for prevention

The study was carried out, as mentioned above, on mice and therefore cannot be extended to humans for the time being. However, the authors went so far as to recruit a small cohort of dengue patients in order to confirm some of these findings.

Not only were mosquitoes preferentially attracted to the odor of people with dengue, but also the latter contained significantly more acetophenone.

This mechanism may represent an effective pathway to prevent mosquito bites. Such an objective, in the West, might not sound like a high priority (after all, in most temperate zones of the planet, mosquitoes are not a major problem today), but we must not forget that climate change is causing the expansion of the habitat of these animals (especially tropical species that are vectors of dangerous diseases) to areas where their presence was previously minimal or non-existent. Of course, they also continue to wreak havoc in many developing nations.

Infectious disease vector control, which includes the use of repellents, fumigation, direct control and appropriate water treatment, is a fundamental tool in the epidemiological approach to these types of infections.

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