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This highly monitored virus carrier is now present in 67 departments in France. Several solutions exist to slow it down, explains the entomologist Didier Fontenille.
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Summer is the best season for the tiger mosquito. Its density increases until September. One in two French people could be bitten this year by the tiger mosquito, at home or at their vacation spot. This estimate is on the rise. We are going to experience a serious public health problem.” Director of research at the Institute of Research for Development (IRD), Didier Fontenille directs the Infectious Risks and Vectors program in Montpellier. The tiger mosquito (Aedes albopictus) can transmit dengue, Zika and chikungunya viruses. To better understand this health nuisance, 120 researchers and international public health actors met at a conference at the IRD last month.
Originally from the forests of Southeast Asia, the mosquito has colonized temperate zones for 40 years. In Europe, it bites in more than 20 countries. Reported in France in 2004 in Menton (Alpes-Maritimes), it now colonizes 67 departments. Mathematical models predicted its expansion, but we were surprised by this speed”. On the website of the Ministry of Health, the presence map in France of the tiger mosquito shows a meteoric rise. From La Rochelle to Strasbourg, regional health agencies are carrying out insect control operations.
In the West, present from Vendée to Mayenne, it is progressing in Loire-Atlantique “where it should become abundant” notes the medical entomologist. The mosquito is also detected in Brittany, where the Regional Health Agency is now strengthening surveillance.
Easily recognizable by its color, black and white striped, Aedes albopictus is original, compared to the 65 other species of mosquito in France, of which 15 bite humans. Not only because it stings during the day, instead of waiting for the night. Its very high genetic variability is quite astonishing. This is one of the reasons why it adapts to very different environments”.
Climate change is not the primary cause of its spread: its colonization follows the highways and main roads. A female enters a car, she comes out further and her eggs colonize another region”. The recent heat wave did not necessarily favor the insect: a study in a mosquito farm showed high mortality above 31 degrees.
Mosquito bites can cause allergic reactions. It is already a nuisance, believes Didier Fontenille, who cites the testimony of people “bitten ten times a day near Montpellier, in Nice, Marseille, and Toulon. It is the main mosquito in town, in the south of France”.
It is the potential transmission of viruses that worries specialists. It is now very low: only 82 people have been bitten in France, in ten years, by a tiger mosquito carrying dengue fever, but also Zika and chikungunya. These “indigenous cases” were contaminated by a mosquito, which had bitten a sick person a few days before, returning from a tropical region where dengue is rife. The number of dengue cases will increase in France, it is inevitable, believes the entomologist, especially as travel has resumed. We expect ten or twenty autochthonous cases this year.”
Hundreds of "imported" dengue cases are also reported each year in France. They are travelers from Overseas, from Reunion where dengue fever has been circulating since 2018 to Polynesia.
How can this nuisance be reduced? The tiger mosquito thrives in small water reserves: the saucer under the flowers, children's toys left in a garden, a poorly cleaned gutter. A first solution, already encouraged in communities in Occitania, consists of emptying all these containers where the water is stagnant.
Several types of traps exist, not always effective, as an ANSES study has shown. Researchers are improving them by studying the behavior of mosquitoes. Another strategy is to release millions of X-ray-sterilized male insects into the wild. Drones carry beakers of sterile males, dropped at sensible locations. They will mate with wild females whose eggs will not hatch."
This method was used in Réunion, as part of a project involving IRD and ARS: 300,000 sterile males released each week reduced mosquito populations by half in a control area. Other scientists atare looking for insecticides of biological origin: viruses that only kill these mosquitoes.
Everyone can participate in the fight against this mosquito. The ANSES reporting portal allows everyone to send their information on the presence and abundance of the insect. These data refine the distribution maps. We can send a photo of the mosquito, more or less crushed. After a bite, no precautions need to be taken, unlike ticks. The chances of being infected with dengue fever are still close to zero in mainland France.
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However, the scorching weather lent itself to a good swim in the sea, this Saturday, June 18, 2022. However, potential swimmers from Urville and Ravenoville (Manche) will have to turn around. Bacteriological contamination forced the municipalities of Sainte-Mère-Eglise and La Hague to issue a municipal decree prohibiting bathing.
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