Pique and pique et colera. The tiger mosquito season has well and truly started. Recognizable by its black and white stripes, this dipteran is now present in three quarters of France. It transmits diseases such as dengue fever, the number of imported cases of which is already reaching records. What are the risks and how can you protect yourself from them? We take stock.
When and how did he arrive in France?
Originally from South-East Asia, the tiger mosquito appeared in mainland France 20 years ago, in the Alpes-Maritimes department. It owes its wide distribution across the globe to international trade. Frédéric Simard, research director at the Research Institute for Development (IRD) in Montpellier, tells Green : “Females lay their eggs on goods stored for export. Arriving at their destination, they can hatch if exposed to rain, and initiate a new invasion. It was thanks to the global tire trade that it moved from Asia to the United States, from where it then invaded the rest of the world.”
Where is it found in mainland France?
Each year, the Ministry of Health publishes a map of the progress and presence of the tiger mosquito on French territory. This insect is gradually establishing itself from the south to the north of the country.
In 2024, the insect has colonized 78 metropolitan departments (out of 96). “The departments are considered to be colonized from the moment when at least one commune in the department is colonized. But there is real heterogeneitypoints out Frédéric Simard of the IRD. In Occitanie and PACA, the majority of municipalities in these departments are concerned while in the north of the country, only one municipality in a department can be.
According to the Ministry of Health, seven new departments have been affected since the beginning of 2024: Morbihan, Moselle, Oise, Sarthe, Seine-Maritime, Yonne and Territoire de Belfort.
As for the rest of the world, it is spreading in France according to commercial flows. “In France, it travels via trade routes, whether by train, boat, plane or truck. This is why the first colonized municipalities are often close to trade routes., according to Frédéric Simard. Hence its absence in certain isolated departments, such as Creuse.
What diseases can it transmit to us?
Mosquitoes are vectors of viruses. “The tiger mosquito is capable of transmitting around fifty viruses, including dengue, chikungunya and Zika. It is the only one in mainland France that can transmit these three viruses.recalls researcher Frédéric Simard.
Fever, body aches… The symptoms associated with these viruses resemble, in the majority of cases, flu symptoms. Conjunctivitis can also be associated with Zika, and nausea with dengue. Frédéric Simard draws a parallel with the Sars-Cov-2 virus: “In the majority of cases, infected people will have few or no symptoms. But, in the case of dengue fever, for example, the most vulnerable people, around 5%, can die from it.”
In Reunion, the tiger mosquito is very present and is the main cause of transmission of these diseases. In Guadeloupe, Martinique and Guyana, a colleague of the tiger mosquito, the Aedes aegypti mosquito, is at the origin of the epidemics that these departments have experienced since the early 2000s. In Mayotte, the two mosquitoes create the risk of propagation of these viruses.
Are many people sick after being bitten?
The tiger mosquito is in the crosshairs of the authorities because it represents a risk of epidemic by passing these viruses to an ever-increasing number of people. Not present in France, these viruses are imported in large numbers each year by people coming from contaminated areas. In 2023, 1,500 imported cases of dengue came from the Antilles. Since January 1, 2024, the number of imported dengue cases has already reached a record, with more than 2,600 cases recorded.
“The mosquito must become infected by biting someone who has been contaminated by a virus in the preceding 10 days or so and carries the virus in their blood. Once contaminated, the female will transmit the viruses to any new person she bites.summarizes the researcher.
“Every year, for a decade, people who have not left the territory have been contaminated by the bite of local mosquitoes, explains Frédéric Simard. The scale and number of these micro-epidemics are increasing year by year, with 40 to 60 cases in 2022 and 2023. We will not be left behind in 2024, and the threat of a large-scale epidemic in the near future must be taken seriously.
What can we do to limit the spread of viruses?
To prevent the transmission of viruses from humans to mosquitoes, the first step concerns “people returning from risk areas; they must protect themselves from mosquito bites,” recalls Frédéric Simard. And this, even if the person is not sick: you can carry a virus without knowing it, without having symptoms; symptoms may take several days to appear.
Other key points: limit the reproduction of the insect. Since the mosquito needs stagnant water for the development of its larvae, it is necessary “pay attention to all places where water can accumulate, such as bowls, flower pot cups, parasol bases, etc. They have to be emptied every week.advises the researcher.
Why is it found more in urban areas?
If the advance of the tiger mosquito may be reminiscent of that of the Asian hornet (our article), which significantly impacts pollinator colonies and competes with the European hornet, the tiger mosquito is neither a predator, nor a competitor to other insects. “It mainly settles in urban areas, where biodiversity is in decline,” explains Frédéric Simard. It can then prosper without risk.
In Europe, this dipteran is present everywhere in Italy and on almost the entire Mediterranean coast, and migrates towards the North.
Illustration photo: AdobeStock
