Anti-mosquito activity already in France amid ‘exceptional’ weather

Anti-mosquito agencies in France are on alert for several species in the east and south of the country following heavy rainfall and mild temperatures in recent weeks.

Forecaster Météo France confirmed on February 23 that France had seen 40 consecutive days of rain of up to 260-460mm in some areas. This has been followed by an exceptionally warm February – the third-warmest on record since 1930, with a new high of 28.3C set in the south-west of France on February 26 (and 130 records set nationwide the day before).

These are conditions that can enable the proliferation of mosquitoes.

Researchers at the anti-mosquito agency l'Entente Interdépartementale de Démoustication (EID) have detected larvae across 6,000 hectares in January and February nationwide, compared to 2,900 hectares last year.

The main species already beginning to emerge is the aedes detritus (saltmarsh mosquito; moustique des marécages or moustique des marais in French). Some areas have also seen the culex pipiens (common house mosquito, moustique commun).

The common mosquito is the ‘typical’ insect that makes a buzzing sound and bites at night. Rainfall and wet conditions help them to thrive, and they can then get into homes and begin biting.

Provence and areas of Grand Est are those most affected so far.

Experts have said that the mosquitoes’ arrival so soon is unprecedented.

“To hatch, mosquito eggs need heat and to be covered with water. With the accumulation of rainfall, the level of wetlands is higher, with larger areas of water and therefore more larvae,” said Pascal Eberhart from the EID, to ICI Provence.

Bio-insecticide has already been employed by the EID as a means of treatment at the start of February, earlier than normal. "We are working to control the situation as much as possible, but in the coming weeks, we will be able to assess the risk,” said Jean-Claude Mouret, head of the Operational Coordination Unit of the EID Mediterranean.

“However it is important to know that we rarely carry out such extensive treatments and on such large areas. We are on to something exceptional."

Common mosquitoes and saltmarsh mosquitoes can be irritating, but they are not dangerous and do not carry diseases.

Tiger mosquitoes on the horizon?

So far, tiger mosquitoes have not made a return, as they only emerge when days get longer. 

“Eggs laid in autumn will only hatch from the end of March onwards, provided that humidity conditions remain favourable,” said Didier Fontenille, Emeritus research director and mosquito specialist at the national sustainable development institute, the IRD (Institut de recherche pour le développment), to La Dépêche.

Tiger mosquitoes differ from the common mosquito in that they are smaller, silent, and bite during the day. However, they are more dangerous as they can be vectors for serious diseases such as dengue fever, Zika, and chikungunya.

People in France are warned to begin preparing for tiger mosquitoes, and to prevent their arrival as much as possible by clearing away any areas that water can collect and remain stagnant. This includes saucers under plant pots, full watering cans, gutters, and other outdoor containers. 

Tiger mosquito traps can also help, but they are “insufficient” said Mr Fontenille. 

Instead, he advised that it is more sensible to do as much as possible to prevent tiger mosquitoes spreading in the first place. “It’s a question of public health,” he said.