Le Figaro Lyon
We will still have to stick to them for several more weeks. Tiger mosquitoes, which drove some Lyonnais crazy this summer, have not finished sucking human blood vintage 2023. The end of the summer period is even the one when the workforce is the most supplied. The metropolis of Lyon will also collect on September 8 the traps distributed to the inhabitants - as part of a voluntary capture operation called Mous'team - in order to assess their presence on the territory. For the record, last year, the exceptional mildness of November had delayed the "traditional" truce, where only eggs remain. Eggs whose stocks were particularly important at the opening of the 2023 season.
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The tiger mosquito does not lay eggs in water but in the open air on a moist substrate, which must be submerged to bring about the hatching of a new generation, "explains Rémi Foussadier, Director General of the Entente interdépartementale Rhône-Alpes de démoustication (EID), the armed wing of the ARS in this area. Last year's droughts have therefore left eggs ahead for 2023. Scissors effect, storms having been more numerous this summer, they allowed more births. "There is a notion of avalanche with the tiger mosquito, the more it goes, the worse it will be, anticipates Rémi Foussadier. The proof, it took him only a few years of presence in France to colonize a large part of the national territory. " The species is now present in more than 70 departments.
" READ ALSO "The French will have to adapt": the tiger mosquito is implanted on three quarters of the territory
The tiger mosquito is now established on most of the French territory. Ministry of Health
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No doubt, I returned to Lyon, I was bitten by a mosquito in the minute I put my foot out of the car, "said Coralie mid-August on Twitter. "It's been an hour that I've been in Lyon and I've already been bitten by a mosquito," announced another user a month earlier. Colonized in 2012, 8 years after the first specimen spotted in Menton, the Rhône is a territory appreciated by the pest. A logical precocity given the frequentation of the department, traversed by major roads while the species was imported according to human activities of tourism and trade.
Aggressive in the heat
Yes, tiger mosquitoes are more numerous this year. And present throughout the territory of the metropolis of Lyon although unevenly distributed. "It's a mosquito that flies badly and moves little," says Rémi Foussadier. It is established thanks to what the inhabitants offer him as a lodging. This is what creates the conditions for its establishment and proliferation. So that, from one neighborhood to another, from one subdivision to another, the population densities are completely different." The tiger mosquito, which used to nest in the hollow of banana trees and other bamboos in the tropics, appreciates tree and rock hollows but especially places regularly watered for egg-laying. Undercutting pots, rainwater collectors and poorly insulated channels are these favorite shelters in France.
It is therefore normal that your colleague who has gone on vacation a stone's throw from your holiday resort has not returned covered with bites. Ditto for your neighbor. Especially since density and nuisance are not correlated for the tiger mosquito which "splits its blood meals", explains Rémi Foussadier, especially in cool hours, which he appreciates. The very ones where his human victims sit on the terrace. "The hotter it is, the shorter the life span of the female, so she becomes more aggressive and stings a lot," says the director of the EID.
Ineffective mosquito control
So, at the heart of the evenings spent scratching under the table, often comes up the question of mosquito control. "It would be totally ineffective, assures Rémi Foussadier from the outset. Treatments act only on adult mosquitoes, not on eggs, the operation should be repeated every 48 hours. On the scale of a city like Lyon, this is infeasible. Besides, no one in the world does it," he objected, further highlighting the effects of the broad-spectrum insecticides used. The only cases of mosquito control occur when a tropical disease such as Zika, chikungunya or dengue fever is detected by a doctor who must report it to the ARS.
"In these cases, we conduct an entomological survey around the places frequented by the patient, then treat on an area of seven hectares around to destroy adult mosquitoes that could have bitten the patient and spread the virus," explains Rémi Foussadier. This was for example the case in the summer, near Lyon, in Couzon-au-Mont-d'Or where a case of dengue fever had been detected in a patient returning from the West Indies. The protocol would be effective enough to limit the number of cases of indigenous transmissions of these diseases to a few units each year. What reassuring, even if the international sporting events to come in France may raise some fears.
Without massive mosquito control, small gestures remain. The ponds planted by Greater Lyon to proliferate dragonflies and other predators of the tiger mosquito, having no real visible impact. The main emphasis of the Government is on prevention in order to avoid creating favourable conditions for proliferation. Put sand in its undercuts, fold its inflatable pool after use, position filters at the entrance of water collectors or silicone pipes to avoid the entry of these small critters of five millimeters. Small simple but essential acts to stem the progression of tiger mosquitoes. Otherwise, they will come back even stronger in 2024.