The Zika virus, tropical flu (dengue fever) or malaria (malaria) are three diseases that have one thing in common: the mosquito ! And more precisely, the mosquito bite of the genus Aedes for the first two and that of its kind Plasmodium for the last. But why do these mosquitoes particularly like the blood of human beings? Scientists from Princeton University in the United States have conducted the investigation and are answering the question!
Mosquito bites: their brain is able to encode the smell of humans
Mosquitoes have very effective targeting strategies, so much so that they are the animal that kills humans the most in the world, with an average of 750,000 deaths linked to a mosquito bite each year. If the war against them is far from won, researchers have made a discovery that could be promising.
“We sought to understand how these mosquitoes distinguish between human and animal odors both in terms of the human scent they spot and the part of their brain that allows them to detect these signals”, explains expert Carolyn (Lindy) McBride, assistant professor of ecology, evolutionary biology and neuroscience, in the study published in the journal Nature.
After several years of research, the scientist and her team have found both answers to this question. “We kind of dove into the mosquito’s brain to ask: ‘What can you feel What activates your neurons? And how is your brain activated differently when you smell a human smell compared to an animal smell?’” explains the researcher. They then used a new approach to understand how the mosquito identifies its next victim using very high resolution imaging of their brain. But not so simple for the team of scientists, since they first had to genetically design mosquitoes whose brains light up when active. The experiments were then carried out in propelling air “with human and animal flavor”in order to analyze how the mosquito detected these two odors.
If human beings all have different body odors, some compounds are present only in our species. Thus, the mosquito’s brain has adapted over the course of evolution to identify and encode them in order to recognize them quickly.
Mosquitoes: developing olfactory traps to trick their brains
“When I first saw the brain activity I couldn’t believe it – only two glomeruli were involved”, said one of the researchers. “It contradicted everything we expected, so I repeated the experiment several times, with more humans, more animals. I just couldn’t believe it. It’s so simple.”
Initially, scientists thought that a very large number of glomeruli (nerve centers in the brain) were involved in this process, but only 2 out of 60 are. The first reacts to many odors including that of humans, while the other reacts only to human scent. Thus, mosquitoes can easily focus on their target. They found that they detected two enriched chemicals in human scent: decanal and undecanal.
Thanks to this information, they patented a mixture composed of decanal which could make it possible to create baits that attract mosquitoes to deadly trapsor even repellents to stop the recognition signals emitted in their brain.