five questions about the proliferation of the tiger mosquito

2023-09-02 14:17:45

Originally from Southeast Asia, the insect is increasingly present in France. After the discovery of cases of diseases he transmitted, several mosquito control operations took place this summer.

Will Ile-de-France residents once once more be able to sleep with the window open without thinking regarding these insects? Two mosquito control operations were carried out in the Paris region, Wednesday August 30 and Thursday August 31, following the discovery of two cases of dengue fever, a disease transmitted in particular by the bite of the tiger mosquito. These operations took place in the 13th arrondissement of Paris, and in Colombes in the Hauts-de-Seine.

Ile-de-France is far from being the only region concerned. Operations have been carried out in recent weeks, once more following the detection of dengue cases, in Lyon, Strasbourg, Toulouse, Mâcon, Poitiers, or Nice. The proliferation of the tiger mosquito and the operations to control this insect raise several questions to which franceinfo provides answers.

1Which departments are affected by the presence of the tiger mosquito?

Of 96 departments in France and Corsica, 71 are currently colonized by the tiger mosquito, reports the Ministry of Health. Only certain territories of the northern half (and Creuse) seem to have been spared for the moment. This mosquito, which has the particularity of biting during the day, is mainly found in urban areas. At the end of 2021, its presence was observed and confirmed in 3,934 municipalities. If you notice its presence in your home, you can report it on the dedicated website. the National Agency for Food, Environmental and Occupational Health and Safety (ANSES).

In some departments, more than 40% of the population lives in a municipality affected by the presence of the tiger mosquito. The South-West, the south-east coast, the Rhône valley, Corsica, the Paris basin and the surroundings of Strasbourg are particularly affected.

2What diseases does the tiger mosquito transmit?

Beyond the itching they cause, tiger mosquito bites can transmit diseases. “The tiger mosquito can be a vector of many viruses such as dengue, Zika or chikungunya”, warns ANSES on its website. To transmit a virus to a person it bites, the mosquito must first become infected by drawing blood from a sick person. In a few days, the virus passes into the saliva of the insect, which contaminates the people it bites. Mosquito control in neighborhoods where a case of dengue fever, chikungunya or Zika has been detected is therefore crucial to preventing an epidemic.

if dengue “is in the majority of cases asymptomatic, (…) in rare cases, serious and sometimes fatal complications may occur”, explains Public Health France. In its classic form, dengue fever “is manifested by high fever, (…) accompanied by chills, headache, (…) nausea, vomiting, joint and muscle pain” in particular, lists the national public health agency. Only 5% to 1% of symptomatic cases may “lead to life-threatening haemorrhages”reassures the agency.

With the proliferation of the tiger mosquito over a large part of France, health authorities are now monitoring “indigenous” cases of this tropical disease, i.e. those contracted without travel, and no longer just “imported” cases. “, as before. In 2022, 66 cases of autochthonous dengue transmission have been documented. “The occurrence of autochthonous dengue cases is now an expected phenomenon in the south of France”estimates Public Health France.

Le chikungunya se manifeste “by a fever and joint pains which disappear spontaneously following a few days”, writes the health agency. Only three episodes of transmission have been observed in France and Corsica. Finally, concerning the Zika virus, a single episode of autochthonous transmission was identified, in 2019. This disease causes in the majority of cases a “rash”a “moderate fever”but also “conjunctivitis, fatigue, muscle and joint pain, headaches”, Public Health France list. In rare cases, the virus can “be responsible for complications” for the embryo or fetus and complications “severe neurological”if the infected person is pregnant.

3What precautions should be taken ?

In order to protect once morest the tiger mosquito, ANSES recommends above all eliminating stagnant water, which are ideal places for the insect to lay eggs and allow it to proliferate. A female mosquito can indeed “lay several hundred eggs with each spawning”. Concretely, the agency recommends “regularly empty or remove the cups under the flower pots, vases… or fill them with sand in order to retain the humidity without there being stagnant water” ; of “store, sheltered from the rain, buckets, gardening equipment, toys or miscellaneous containers” ; of “cover the water collection containers with a mosquito net or fabric” ; and of “clean the gutters to facilitate the proper flow of water”.

If tiger mosquitoes are present, you can still limit the risk of being bitten by adopting these actions recommended by ANSES: “wear long, loose and light-colored clothes”, “use skin repellents following the precautions for use indicated”, et “ use mosquito nets”. As for mosquito bracelets, which contain chemicals, the health security agency recommends proscribing them in infants and young children, following several cases of burns.

4 How does a mosquito control operation take place?

Mosquito control operations are not carried out systematically when the presence of tiger mosquitoes is discovered. These operations “are only triggered by the health authorities in the event of a risk of epidemic spread of dengue fever, chikungunya or Zika”, explains the regional health agency (ARS) of Auvergne-Rhône-Alpes. When a person is affected by one of these three diseases, an investigation is carried out to determine the area to be mosquito controlled. “This is to prevent tiger mosquitoes present from biting the sick person and transmitting the disease to other people around.explains the ARS.

L’mosquito control operation then takes place at night, “to avoid the presence of people outside on the treated area and minimize its impact on other insects”. A document is distributed to the population of the district concerned. “Although the product and the dosage used are without risk for the population, it is strongly recommended to follow the precautions listed on the flyer distributed in mailboxes or displayed in buildings”, recommends the ARS. A biocidal product is sprayed to kill larvae and adult mosquitoes.

5Is the proliferation of the tiger mosquito related to global warming?

The proliferation of the tiger mosquito raises the question of the presence of the insect in Europe. How does this insect, native to Southeast Asia, manage to thrive in our latitudes? “It’s partly linked to climate change”explains Céline Bellard, researcher in ecology at the CNRS, interviewed by France Télévisions.

The scientist thus points the finger “winters that are milder, and temperatures that are milder, earlier in the year”. This situation “allows a period of nuisance to the tiger mosquito which is much greater than what was observed before”.

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