Photo by Егор Камелев on Unsplash

Pasteurdon 2022: Investigating new virus transmissions to humans by mosquitoes

Zika, dengue fever, yellow fever, chikungunya… All these diseases are transmitted to humans through the bite of infected mosquitoes.

These mosquitoes are enormous virus reservoirs, as a single mosquito contains billions of virus particles, which can come from multiple viruses pathogenic to humans.

Contact between humans and mosquitoes cannot be avoided; on the contrary, these contacts increase with deforestation, rising temperatures and high population concentrations.

Under our windows, on our balconies or in our gardens, the water cups of our green plants are places where mosquito larvae develop. And we humans are an inexhaustible source of protein during the breeding season for female mosquitoes, who sting us with a few microliters of blood. explains Anna-Bella Failloux, entomologist and virologist, head of the Arbovirus and Insect Vector Research Unit at the Pasteur Institute.

Of the approximately 3,500 mosquito species identified, only 15% bite humans. Three mosquito species are the main vectors of viral diseases in humans: the tiger mosquito or Aedes albopictus, Aedes aegypti or Culex quinquefasciatus.

There are few solutions to effectively combat these mosquitoes. The use of insecticides is not very effective because the active molecules used are not very different and resistance occurs
quickly into mosquitoes. In addition, this solution has harmful environmental effects for other species.

Today there is no silver bullet and we must continue and intensify research efforts to better understand the transmission of these diseases. We know little about how the virus emerges from the animal reservoir and spreads from animals to humans explains the researcher.

And to add: the link between these two hosts is the mosquito. We know the city’s mosquitoes very well because we breed them and can therefore study them in the laboratory. On the other hand, in captivity, in laboratories, the wild mosquitoes, which are the source of virus formation, cannot survive. So we know very little about them. “.

Within the Institut Pasteur, no fewer than four research units are actively working to remove these obstacles and to understand the genesis processes of vector-borne diseases in humans, in particular by drawing on all the expertise and necessary observations of other teams present on campus and in the Pasteur network.

Despite the very advanced technologies available, observation both in the field and in the laboratory remains essential to understand the mechanisms of transmission of the virus by the mosquito and the evolution and replication of the virus in its host.

There are still a large number of mosquito species to be identified, the greatest diversity of species can be found in tropical forests: ” More than 235 species are listed in Madagascar and a variety of viruses are kept in wild cycles. The field work consists of following the emergence of viruses from these protected areas of biodiversity. Comprehensive monitoring of these forests makes it possible to predict the emergence of epidemics and better understand the chain of transmission of the virus. », emphasizes Anna-Bella Failloux again.

His laboratory houses an insectarium within the Pasteur Institute to breed mosquitoes and study tiger mosquitoes in particular.

All biological disciplines are represented on campus, making it the best place to study infectious diseases. My research combines entomology and virology, an essential dual discipline not necessarily known to the general public. ‘ she concludes.

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