From May 1 to November 30, which corresponds to its main period of activity, the health authorities will scrutinize the presence of Aedes albopictus – its scientific name -, multiply awareness messages and trigger possible mosquito control operations.
Because last summer, the tiger mosquito, recognizable thanks to its black and white stripes, left a bad memory. As of January 1, 2023, it had colonized 71 departments, a number that has been constantly increasing since its installation in France in 2004.
And the insect, which bites more in the morning and in the evening, was the cause of 65 “indigenous cases” of dengue fever, concentrated in the south of France: the term designates patients who have not traveled to areas where the virus circulates widely, such as the West Indies, but were bitten by a mosquito that infected itself through contact with an infected traveler.
“65 cases may not seem like a lot, but it shows a dynamic, it’s a signal for the future”warns Marie-Claire Paty, vector-borne disease surveillance coordinator at Public Health France.
In fact, since 2010, the number of metropolitan departments colonized by the tiger mosquito has multiplied by ten.
“We are convinced that this is a risk that will intensify”insists Ms. Paty.
“inevitable expansion”
This is also the message conveyed by the Health Risk Watch and Anticipation Committee (Covars), the former scientific council, in a recent opinion.
We must expect, in the years to come, an increase in cases of dengue fever, Zika and chikungunya, diseases transmitted by “vector” mosquitoes now widely established on the national territory, he warned. Viral diseases which “could become public health problems”.
If, in mainland France, a serious form has not been observed to date, complications are always possible, which can lead to resuscitation or even death, recalls Marie-Claire Paty.
In Ile-de-France, it is now definitively established in around a hundred municipalities.
“Its extension is inevitable”, says entomologist Didier Fontenille. “It is an urban insect, which travels in cars and lays its eggs in collections of water” left by people – breeding sites – such as pots, saucers, water collectors. “He likes human blood, which in town, there is no shortage of”he continues.
To make matters worse, global warming has indirect effects on its growth: the hotter it is, the shorter the mosquito’s development cycle.
The multiplication rate of the virus inside the insect is also increased under the effect of temperature. “So the hotter it is, the faster it can transmit an infection”explains Anna-Bella Failloux, specialist in mosquito-related diseases at the Institut Pasteur.
“To live with”
However, its expansion remains essentially favored by travel and human behavior. The health authorities thus fear the forthcoming organization of major international sporting events in mainland France – in particular the 2024 Olympics -, which will give rise to significant movements of populations from all over the world.
“If in the overseas territories the tiger mosquito transmits a lot of viruses, it remains for the moment in mainland France an essentially harmful insect. But that could change in the years to come”advises Didier Fontenille.
To limit the risks“the first thing to do is to make life difficult for him”, advises this research director at the Research Institute for Development (IRD) in Montpellier.
“Overseas, the mosquito is already part of everyday life. In France, we will now have to learn to live with it”summarizes Anna-Bella Failloux.
Eliminate all places where water can stagnate, empty containers, cover reservoirs and swimming pools when they are not in use… here are just a few things to do, both by individuals and territorial agents.
Some repellents can also be useful, but not all are optimally effective against the tiger mosquito.