How do mosquitoes sniff us all the time?

Mosquitoes always achieve their end: to pump our blood to feed their eggs. If they are so effective in detecting us despite our efforts to repel them, it is because they have an extraordinary olfactory system.

No matter how much we do to protect ourselves from it, the mosquitoes always end up biting us. They are attracted by our smell, CO₂ that we expire but also some colors. With so many parameters, theequation to avoid bites becomes hard to solve, even spraying on mosquito repellent doesn’t seem to have any effect. And for good reason, their olfactory system is organized in such a specific way that they cannot miss us, despite our efforts to repel them.

This study, published on August 18 in Cell, brings together several teams from various American universities, all led by Boston University. Their work starts from an observation: if manipulating Genoa involved in vision mosquito makes him “blind”manipulating those in his olfactory system has little effect – even deprived of some sense of smell, they sting again and again.

The “terribly weird” nose of mosquitoes

And for good reason, the olfactory system of mosquitoes is “terribly weird” in the words of Meg Younger, mosquito specialist and principal investigator of this study. The olfactory system is, according to the canonical vision, composed of a set of neurons olfactory which each express a single receptor for a family of molecule olfactory. A neuron corresponds to an odor.

Meg Younger and her collaborators show that in mosquitoes, the organization of the olfactory system is much more complex. An olfactory neuron can express several odor receptors at the same time. Thus, mutating the gene encoding the CO receptor₂ – a major sign for the mosquito of the presence of a human or other animal – does not prevent them from finding their target, because other genes take over in detecting odors.

This research was carried out on mosquitoes from thespecies Aedes aegyptiprobably one of insects the deadliest. Indeed, a harmless bite in most cases can become fatal when it causes contamination by a virus pathogenic. Aedes aegyptias Aedes albopictus with which it is often confused, and which resembles what is called the tiger mosquitois the vector of Zikaof the dengue fever and chikungunya. These diseases, called arboviruses, claim more than 700,000 victims each year.