By David Saint Sernin
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These are the first cases of autochthonous dengue fever of history in Haute-Garonne. For a week, the municipality of La Salvetat-Saint-Gillesnear Toulouse, must manage the arrival of this disease linked to the presence of mosquitoes.
Mosquito control operations
Within a few days, three mosquito control operations took place in this municipality in well-targeted areas.
Blagnacdue to a case of imported dengue, and Toulousefor a suspected case of dengue fever, also carried out special mosquito control operations.
The residents of the agglomeration exasperated
On social networks, these operations have had the gift of get residents to react of the agglomeration, visibly exasperated by the general invasion of mosquitoes on the territory of Toulouse Métropole. Little anthology…
For Satine, “they are waiting for dengue fever to arrive and we, north of Toulouse, are getting eaten up…”.
For Lily, “removing mosquitoes from a street is absolutely useless”. She adds: “It’s the whole town that needs mosquito control. At the end of the summer, it’s a little late, it’s around March-April that you have to do it”.
” TO Colomiers, it’s for when ? asks Josette.
ToCastelginestin Aucamville, Launaguet, Saint-Orens, Pibrac… Always the same observations: “We are infected, “it’s total invasion”, “it’s hell, we can no longer enjoy the gardens, nor take a meal outside
Camille sums up everyone’s thinking behind the devastated messages: “But in fact, it is the whole enlarged agglomeration that should be mosquito-removed to restore a semblance of serenity to Toulouse residents…”
To remove mosquitoes from an entire municipality, like some municipalities on the Mediterranean coast, or even the entire agglomeration? It would be very complicated, for various reasons, answers the Regional Health Agency of Occitanie.
“Empty a bathtub with a spoon”
According Jean-Sebastien Dehecq, sanitary engineer at ARS Occitanie, removing mosquitoes from a large area of the Toulouse agglomeration in the spring would be like emptying a bathtub that is filled with a spoon…”. He explains:
“The mosquito develops in two stages. The eggs laid in the water become larvae, then the mosquito emerges. However, mosquito control, as it is practiced, does not completely eliminate the larvae in the water in spring or early summer. Then, during the summer, and especially in August and September when the mosquito population is the most numerous, generalizing the mosquito control operations in all the municipalities of the agglomeration, and carrying them out on a regular basis, would then haves harmful consequences. Indeed, the product used is not selective and twould kill other insects than mosquitoes. And if it rained, the dispersed product would run off into the water of the streams and also kill aquatic fauna”…
For all these reasons, the “exceptional operations” currently being carried out in the Toulouse conurbation, due to the circulation of dengue fever, require a few precautions: study of the treated site, identification of possible watercourses, since cannot disperse the insecticide less than 25 meters from a stream or a river, identification of organic farming plots that cannot be treated…
Very supervised global mosquito control
According to the ARS, the municipalities could nevertheless opt for mosquito control on the adult mosquito, but used with parsimony“as some municipalities in Languedoc do before holding a major event on their territory, for example”.
Operations that can only be ad hoc, and targeted by municipality, because of their harm to the environment, but also because by using them regularly, they would accentuate mosquito resistance. Above all, they are very strictly supervised by the authorities, in particular the prefectures.
Despite the complexity of the fight, some municipalities are trying things. To Colomiers for example, each year, three anti-larval treatments are carried out on 18 storm basins and bodies of water in the municipality.
In 2022, the first campaign took place at the beginning of May, a second took place at the end of June-beginning of July and the third was to take place at the end of August-beginning of September.
“These treatments, carried out with a biological product, are safe for humans and the surrounding fauna and flora. This action is carried out by a specialized service provider, as part of an annual public pest control market (mosquitoes, Asian hornets, processionary caterpillars and pigeons)”, explains the municipality.
Some municipalities mix the measures
In recent years, other municipalities have tried anti-larval treatment, such as Balma and Cugnaux.
Some have mixed several solutions, such as Blagnac, with the installation ofe nest trapsthe establishment of mouse-saving nesting boxes and the use of biological treatments.
In addition to this mix of measures at municipal level, the ARS obviously insists on the everyday gestures which, carried out by each inhabitant, can make it possible to limit multiplication mosquitoes : eliminate places where water can stagnatelimit bulky waste as much as possible, change the water for plants and flowers once a week, or remove saucers from flower pots, replace the water in vases with wet sand, check for proper water flow rain and sewage and regularly clean gutters, manholes, gutters and drains, cover water tanks with a mosquito net or a simple fabric, cover the swimming pools…
At ARS Occitanie, Jean-Sébastien Dehecq reminds us: “The mosquito moves very little in his life, between 30 and 50 meters. If you have mosquitoes at home, it’s because they come from your property or from very close land. Everyone can therefore act for themselves or for their neighbours…”
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