French, Swiss and Germans partner up in fight against disease-spreading tiger mosquito

Nothing is better for mosquitoes than a dark, warm and humid place. Given that heat records have been broken in recent summers, the spread of the tiger mosquito is, according to the National Assembly's report, "inevitable throughout France". [frank60/shutterstock]

Faced with the rapid rise in disease-spreading tiger mosquitoes, a team of French, German and Swiss scientists have combined forces and knowledge to halt their expansion. EURACTIV France reports.

In France, a small and bloodthirsty insect, known as the tiger mosquito, is currently at the heart of the debate. Named for its black body with whitish scales, this insect native to tropical Asia is now well established in several southern European countries.

According to the latest report of the French National Assembly in July 2020, these insects pose a “major health risk”. In 2019, the insect ‘colonised’ 58 of the 96 departments of metropolitan France.

Present mainly in the south of the country and in the Île-de-France region, Aedes albopictus  also seems to appreciate the shady banks of the Rhine, since it can be seen in Alsace, in the German province Baden-Württemberg and in Switzerland.

In 2018 a group of French, German and Swiss scientists launched a transnational project in the Upper Rhine basin, known as the Tiger project.

“Tiger aims to jointly monitor the spread of the tiger mosquito and to combine research for better containment,” said Bruno Mathieu, a medical entomology researcher at the University of Strasbourg and coordinator of the Tiger project.

Each year, traps, in which the mosquitoes will lay their eggs, are placed at the same time on both sides of the border.

“This allows us to see where the tiger mosquito is located, and to then draw up maps. The tiger mosquito was first seen in Baden-Württemberg in 2011, before moving to Alsace, particularly in the Bas-Rhin since 2014, and to a lesser extent to Switzerland,” Mathieu added.

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Global warming’s big winner

Nothing is better for mosquitoes than a dark, warm and humid place. Given that heat records have been broken in recent summers, the spread of the tiger mosquito is, according to the National Assembly’s report, “inevitable throughout France”.

First seen in Albania in 1979, the tiger mosquito has since migrated up the Balkan peninsula to the Italian boot, before spreading to France, Spain, Switzerland and Germany.

And the cold doesn’t seem to hold the insects back.

“At the beginning of our research, we hoped that the harsh winter in our regions would harm the insect’s eggs, but that’s not the case,” said the researcher.

In addition to climate change, which will push the tiger mosquito further north, it is above all human activities that are enabling the species to settle permanently in new territories.

We now know that the tiger mosquito arrived in Europe through the tyre trade,” said Mathieu. “The insect lays its eggs in tyres. The eggs are then transported from one country to another, before hatching upon the first rainfall. Sometimes on the other side of the world,” he added. This exodus may be poetic, but the tiger mosquito is a carrier of tropical diseases including dengue fever, chikungunya and the Zika virus.

These deadly diseases oblige the authorities to deploy control devices to closely monitor the tiny bloodsucker that is no bigger than a penny.

In addition to the nesting traps, France’s National Health Security Agency (Anses) has set up a portal for reporting the tiger mosquito. The tri-national Tiger project has also taken up this initiative.

“Our neighbours across the Rhine did not have such a website. To be consistent, we developed the same reporting system. It’s a form that can be filled out in both languages, in French and German,” according to the Strasbourg-based researcher.

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“Social mobilisation”

Eradication of the tiger mosquito, however, seems unlikely.

As the report of the National Assembly points out, for “almost all insecticide products, excessive use increases the risk of the development of resistance to the product in mosquitoes,” which would “considerably reduce the effectiveness of treatments.”

“Social mobilisation”, according to the report, remains the best control strategy, a view which has been backed by Bruno Mathieu, for whom “education is the key point in the fight against the spread of Aedes-type mosquitoes.”

With this in mind, the Tiger project has equipped its website with a kit for use by school and college teachers, and travelling exhibitions and training courses are organised for local authorities and town halls. The project, which benefits from EU funding, will come to an end at the end of 2020, however.

At present, scientists from the six partner research institutions are hoping to obtain new funding to continue their research and perpetuate what has been achieved in the Upper Rhine region.

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