“Temperatures are increasing, living conditions are deteriorating: we are creating conditions for the development of mosquitoes adapted to life with humans“, underlines entomologist (insect specialist) Anna-Bella Failloux, who heads the Arbovirus and insect vectors unit at the French institute.
His team is working on “the species of mosquitoes that live in the city with us: initially, they developed in tropical forests, taking blood from animals; today, they lay eggs in the city in a plastic bucket of water, next to people they sting“, she summarizes.
Today, 80% of the world’s population runs the risk of being exposed to one or more infectious diseases long considered tropical, which kill more than a million people per year, mostly children, according to the World Health Organization. Health.
Transmitted by a mosquito from the Anopheles family, the deadliest, malaria, caused 608,000 deaths in 2022.
To study them, the Pasteur Institute announced on Tuesday that it would invest 90 million euros to build a “research center on infections linked to climate and environment“, which will emerge from the ground in 2028 in the heart of its historic site in Paris and will house innovative research in secure laboratories.
“This will allow us to have all species of mosquitoes at the same time, in the same place“, explains Anna-Bella Failloux, showing us around the much more modest premises which, for the moment, host her insectarium.
Twenty-eight degrees and 80% humidity: in a cramped room in the basement, the conditions are ideal for breeding, in plastic trays on shelves, mosquitoes from all over the world: Florida, Gabon, Nigeria, Thailand, Taiwan, New Caledonia…
“Tips to attract them”
Out of 3,500 species of mosquitoes, only 15% bite humans. “Those that interest us are the Aedes aegypti and the Aedes albopictus (the tiger mosquito), which live where there is a significant human concentration and water which stagnates around houses due to lack of evacuation, as in the favelas of Rio“, describes the entomologist.
If these two species are responsible for the transmission of several diseases to humans, many questions remain unanswered.
-“Today, the malaria mosquito, Anopheles gambiae, cannot transmit the viruses of yellow fever, dengue, chikungunya, zika, etc. even though it coexists with Aedes aegypti, which transmits them.“, continues Ms. Failloux.
“They live in the same place, bite humans in the same way, so how come only one of them transmits malaria? We would like to address these kinds of questions“, she said.
To study the transmission of these viruses, researchers infect female mosquitoes – the only ones to bite -. They are first “starved for 24 hours”, then “we fill a capsule covered with skin – generally pig intestine – with a mixture of blood and virus, which the female mosquito will come and bite“.
“The difficulty“, explains the researcher with a mischievous smile, “it’s to force them to eat, because it’s not very appetizing. So we have lots of tips to attract them: we wear smelly socks, CO2, or the smell of apples“. Et “some only bite at night: we have to infect them in the dark, so it’s complicated“.
Within three years, this research should make it possible to draw up “risk cards“for the tiger mosquito, present on 80% of French territory, by testing”different populations of mosquitoes against 12 distinct viruses“.
“This would tell us that in this given region, with such a density of mosquitoes and such a virus coming from Martinique or elsewhere, we are on red alert“. “Today, it is unknown whether all regions have the same risk of having chikungunya, dengue or zika, if there is an imported case“, explains Ms. Failloux.
As mosquitoes have developed resistance to insecticides, “we must make a fight that is as targeted as possible“, she concludes.
