Dengue mosquito proliferates in France and could cause epidemics in the coming decades

Dengue can be transmitted by mosquitoes Aedes aegyptithe most common in Brazil and Guaiana, for example, and at least Aedes albopicus, known as the Tiger mosquito, present in North America and Europe, including France. The country already records indigenous cases, that is, cases that were not imported.

“The Tiger mosquito arrived in Europe in 1990 and in 2004 in France. Twenty years later, it is present in all regions of the country and is not going to disappear. Its own biology forces it to remain in the territory to survive”, explained Anna-Bella Failloux, responsible director of the Arbovirus and Insect Vectors Unit at the Pasteur Institute in Paris, to the program Priority Santéfrom the RFI.

According to her, the Aedes aegypti and the albopicus are invasive species. “Tiger mosquito eggs are able to withstand drought and low temperatures in winter. He waits for good weather conditions for the eggs to hatch and transform into adult larvae, which are responsible for transmitting certain viruses.”

Will Europe then be able to face dengue epidemics in the coming decades, like Brazil? For the specialist from the Pasteur Institute, the Tiger mosquito will continue to colonize the continent, which will favor the circulation of the virus and generate more and more autochthonous cases, that is, contaminations that occur when two people become ill within the territory itself.

According to Anna-Bella Failloux, another problem is that the European population is less prepared to fight the dengue mosquito and ignores certain reflexes already acquired in other countries, such as not leaving standing water in a container, for example.

Climate change and human activity

How and why are vectors spreading so quickly across the planet? Global warming, but also human activity, partly explains the situation, says the scientist at the Pasteur Institute.

“Human activities are the first cause of the proliferation of mosquitoes and the viruses transmitted by these mosquitoes. These insects live where there are people. So, from the moment we live on the ground floor, in cities, and maintain suitable places for these mosquitoes to reproduce and bite humans, we create an explosive cocktail that will generate the emergence of urban cases”, he says.

Demographic growth, he highlights, also creates an environment favorable to the disease. Half of the world’s population, notes Anna-Bella Failloux, lives in cities and is often exposed to precariousness.

Problems with storage, evacuation and drinking water supply are also factors that facilitate mosquito reproduction. There is also global warming, which changes the insect’s mobility, causing it to colonize more and more regions of the northern hemisphere.

Four types of viruses

There are four types of dengue virus, which use mosquitoes as vectors. “They behave differently in relation to the insect, which will not transmit the four pathogens with the same efficiency. This makes some combinations, depending on the type of virus and mosquito, more effective”, explains Anna-Bella Failloux.

Some infections progress to more serious forms, such as hemorrhagic, and can cause complications. Warning signs are edema throughout the body and bleeding. But despite these risks, these situations are relatively rare and mortality related to the disease is low, representing less than 5% of cases.

French infectious disease specialist Paul Le Turnier works at the Cayenne Andrée Rosemon Hospital Center, in French Guiana. He recalls that the Qdenga vaccine, already used in Brazil, should soon also be available in Guyana, which will be an effective way to fight the epidemic.

Besides vaccination, the only way to fight the mosquito is mechanical, stresses Le Turnier. That is why it is important to educate the population and carry out pest control campaigns. Furthermore, treatments are evolving. “There are therapeutic leads with new antivirals, but they should only be available within many years.”