They say that mosquitoes are the deadliest animals for humans. Even more than people themselves. Mosquitoes are often another summer nuisance, but their ability to transmit diseases such as malaria or dengue requires researchers to pay close attention to them.

It is important to understand why they itch. We know that it is females who do this to obtain food during their breeding process, but how do they choose their prey? That’s the question asked by an international team of scientists who published their results in an article in the journal Nature.

Aedes aegypti: specialized in humans. The team focused on a specific type of mosquito, dengue fever, or yellow fever (aedes aegypti). This mosquito species is interesting for two reasons. The first is its danger and, implicitly, that it is a vector of diseases such as the Zika virus. Although most mosquitoes will attack any animal they can, this species is specialized for humans.

What were they looking for? The study had two axes. On the one hand, he tried to find out exactly which compound the mosquitoes reacted to. Human odor is a mixture of chemicals floating in the air. None of these components was able to produce a response from the insects by itself. Therefore, they tried to combine several of these compounds. So they discovered that what triggers the response in mosquitoes is a combination of two odor-related molecules (decanal and non-decanal adhesides) that we secrete in humans.

looking for answer. The next axis of the study was based on searching in the insect’s brain which regions responded to the stimuli. According to Carloyn McBide, Princeton University and the scientist responsible for leading the study, researchers* asked what a mosquito can smell by entering its mind* and why it is activated differently when smelling humans or other animals.

To answer these questions, they turned to the CRISPR system, in which they genetically modified the mosquitoes so that their brain’s response to stimuli was visible.

Great results. The team was “surprised” by the results, as they thought that a biological function as important as foraging would require very complex work in their brains. That was not the case. The brains of these mosquitoes have 60 different areas. Each of these areas is a nerve center called the glomerulus. What the scientists did was observe which of these glomeruli “light up” when mosquitoes sniff out humans.

The team expected that most of these 60 glomeruli would be activated by smelling humans, but only two did. Specifically, one of these glomeruli was activated by the scent of different mammals, which is a way to draw the animal’s attention to a scent that might be interesting. The second of these nerve centers was activated only in response to strictly human odors, and that’s when it began to satisfy the mosquito’s appetite.

Where do these mosquitoes live?. Although there are infections associated with the tropics, countries such as the United States are within the habitable zone of these mosquitoes, particularly the southern United States and areas in the southern half of the Atlantic and Pacific coasts. For now, these mosquitoes have not been observed in Spain, but there is a surveillance and warning mechanism to control their possible arrival. One of many mechanisms to keep these mosquitoes from settling in Europe, as do tiger mosquitoes (Aedes albopictus).

A new tool to control these types. The team also proposed a mechanism to overcome the mosquito problem, and it’s a type of bait based on what was discovered in the study. Knowing that the combination of decanal and undecanal can attract these mosquitoes, the researchers patented a mixture of these chemicals for use in insect traps or repellents.

Image: Mohammed Mahdi Kerim