They say that mosquitoes are the deadliest animals for humans. More even than humans themselves. Mosquitoes are generally just another summer nuisance, but their ability to transmit diseases such as malaria or dengue fever requires researchers to pay close attention to them.
Understanding why they itch is important. We know that it is the females that do it to obtain nutrients in their reproductive process, but how do they choose their prey? That is the question asked by an international team of scientists who have 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 or yellow fever (Aedes aegypti). This type of mosquito is interesting for two reasons. The first is its danger, and it is that, as can be intuited, it is a vector of diseases such as the Zika virus. While most mosquitoes 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 what compound the mosquitoes reacted to. Human scent is an amalgamation of chemicals floating in the air. None of these components was able by itself to generate a response from the insects. For this reason, they tried to combine several of these compounds. They thus discovered that it was a combination of two odor-related molecules that we secrete in people (decanal and undecanal adhesids) that triggered a response in mosquitoes.
Looking for answers. The next axis of the study was based on searching in the brain of insects which areas reacted to stimuli. According to Carloyn McBide, a scientist at Princeton University and responsible for leading the study, the researchers * got into * the mind of the mosquito to ask what it can smell and why it is activated differently when smelling human aromas or of other animals.
To answer these questions, they turned to the CRISPR system, with which they modified the genetics of the mosquitoes so that the reaction of their brains to stimuli was visible.
Amazing results. The team was “surprised” by the results, since they imagined that a biological function as important as looking for food would require a very complex job on the part of their brains. It 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 “lit up” when the mosquitoes smelled 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 smell of different mammals, a way of attracting the animal’s attention to a smell that could be interesting. The second of these nerve centers was activated only in response to strictly human odours, and that is when the mosquito began to satisfy its appetite.
Where do these mosquitoes live?. Although they are infections that are related to the tropics, countries like the United States are in the habitable zone of these mosquitoes, specifically the southern United States and the areas in the southern half of its Atlantic and Pacific coasts. For now, these mosquitoes have not been observed in Spain, but there is a surveillance and alert mechanism to control their possible arrival. One of many mechanisms to prevent these mosquitoes from settling in Europe, just as the tiger mosquitoes (Aedes albopictus) did.
A new tool to control these species. The team also proposed a mechanism to tackle the mosquito problem and it is a kind of decoy based on what was discovered in the study. Knowing that a combination of decanal and undecanal is capable of attracting these mosquitoes, the researchers patented a mixture of these chemicals to be used in insect traps or repellents.
