Pasteurdon 2022: studying new virus transmissions to humans by mosquitoes

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

These mosquitoes are enormous reservoirs of viruses since a single mosquito contains billions of viral particles which can be derived from several viruses pathogenic for humans.

Impossible to avoid contact between humans and mosquitoes, on the contrary, these contacts are multiplying with deforestation, rising temperatures and high population concentration.

Under our windows, on our balconies or in our gardens, the water cups of our green plants are places where mosquito larvae develop. And as humans, we are an inexhaustible source of protein food for female mosquitoes in the breeding season, which puncture us with a few microliters of blood during a bite. explains Anna-Bella Failloux, entomologist and virologist, head of the Arbovirus and insect vector research unit at the Institut Pasteur.

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

Few solutions exist to effectively control these mosquitoes. The use of insecticides is not very effective because the active molecules used are not very varied, and resistances appear
quickly in mosquitoes. In addition, this solution has a harmful environmental impact for other species.

Today, there is no single solution 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 crosses from animals to humans explains the researcher.

And to add: the link between these two hosts is the mosquito. We know the mosquitoes of the city very well because we can breed them and therefore study them in the laboratory. On the other hand, the wild mosquitoes at the origin of the viral emergence cannot survive in captivity, in laboratories. So we know very little about them. “.

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

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

There are still a large number of mosquito species to be identified, the greatest diversity of species is found in tropical forests: ” In Madagascar, more than 235 species are listed and a multitude of viruses are maintained within wild cycles. Field work consists of tracking the emergence of viruses from these sanctuaries of biodiversity. Extensive monitoring of these forests makes it possible to anticipate the creation of epidemic outbreaks and to better understand the chain of virus transmission. », Emphasizes Anna-Bella Failloux again.

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

All biological disciplines are present on campus, making it the best place to study infectious diseases. My research combines entomology and virology, an essential double training not necessarily well known to the general public. “, she concludes.

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Pasteurdon 2022: studying new virus transmissions to humans by mosquitoes

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