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France fighting dangerous tiger mosquito

Tiger mosquito now reaching the north of Paris

Scientists are closing in on a method to reduce the mosquito populations as health authorities warn the tiger mosquito has spread to 42 departments, now reaching to the north of Paris.

Genes of a bacteria that makes the female common mosquito sterile have been studied by a team from Montpellier university who have found the genetic mechanism behind it.

This could open up a way to reduce the spread of mosquito-borne diseases such as dengue, zika and chikungunya.

The bacteria, Wolbachia, is  normal in mosquitoes and if an infected male mates with a non-infected female the eggs are sterile. However, eggs survive if the female is also infected so, after time, only infected insects remain.

Tests in Asia, Latin America and Australia have seen infected males and females released to breed with wild mosquitoes. However, this will eventually lead to non-infected mosquitoes being replaced by infected ones.

The bacteria is safe for humans but mosquitoes that carry it have a reduced ability to transmit dangerous viruses.

Researchers at the Institut des Sciences de l’Evolution (Mont­pellier) published their results in Nature Communications. One of the project leaders, Mathieu Sicard, told Connexion they had identified a protein that caused the sterility and shown that the bacteria had many variations that could be used to obtain a good weapon against one ‘focal’ mosquito population.

“For instance, the bacteria in mosquitoes in Tunisia is different from that of mosquitoes in France and it will cause sterility if the two mate.

“The problem now is to find a way to create many more infected males without releasing infected females at the same time, but this is not the topic of my present research.”

The World Mosquito Prog­ram says 40% of the world’s population is at risk from dengue which sees 390m infections a year. Zika affects 84 countries and a case of chikungunya is confirmed every four minutes.

The Montpellier researchers work was on the common mosquito but Wolbachia bacteria is also carried by the tiger mosquito and it is hoped this will give a new means of control.

Climate change is helping the spread of tiger mosquitoes since they arrived in Alpes-Maritimes in 2004. They now cover all of the south to as far north as Alsace and Aisne and are in the UK.

The national health authority La Direction Générale de la Santé said tiger mosquito numbers had doubled in the past two years in France, making it a “priority target for surveillance”.

Authorities say if a tiger mosquito is found in your garden or home there is an 80% chance it was raised there or nearby. Res­i­dents should empty containers holding water that can go stagnant, where females lay eggs.

This includes gutters, toys and plant-pots – or fill these with sand to allow watering but leaving no standing water. Rainwater butts should be covered.

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