Dengue fever: a study shows the deviant behavior of mosquitoes carrying the virus

Scientific work has revealed that mosquitoes carrying dengue fever lose part of their reason. The insect would therefore be subject to the virus, which would increase the risk of transmission to humans. Explanations.

Surprising discovery. Carried out in collaboration between French and Singaporean researchers, scientific work shows the change in behavior of Aedes aegypti, female mosquitoes that prey on humans. When they are infected with the dengue virus, they go into a daze, as if “manipulated” by the virus, and they would lose part of their reason.

Strongly present in Overseas France, particularly in Reunion and the West Indies, the dengue virus causes 400 million infections and 25,000 deaths each year, according to the Institute for Research and Development (IRD). Julien Pompon, researcher at the MIVEGEC laboratory in Montpellier, supervised and coordinated this study for three years on the behavior of mosquitoes. The scientist noticed that the actions of the Aedes aegypti were particular when they are previously infected: “We also know that the mosquitoes that transmit malaria have their behavior changed once infected. We asked ourselves the question for the dengue virus, do infected mosquitoes have a changing behavior?”

The study was conducted on a hundred mosquitoes, half of which were infected with dengue fever. “We built small cages in which we put a mosquito with a sleeping mouse. Using a high-definition camera, we were able to precisely observe its behavior, of which we obtain a general view”explains Julien Pompon.

The Aedes aegypti become “distraught”, according to the scientist. “It has been observed that infected mosquitoes were more attracted to mice, which means that these mosquitoes will come closer to a human host to bite them more. Second observation, infected mosquitoes need to bite several times to arrive to draw the same amount of blood as uninfected mosquitoes.”

With each bite of an infected mosquito, even a short one, there will be transmission of dengue fever.

Julien Pompon, researcher at MIGEVEC

In this case, transmission of the dengue virus would be three times higher than normal. “It’s exponential”, adds Julien Pompon. “Finding that the number of bites increases with the mosquito’s infection was not obvious, that’s the discovery. The game of evolution caused the virus to mutate to change the behavior of the mosquito in order to optimize its transmission.

The explanation lies in the fact that the mosquito does not arrive “at the blood meal”explains Julien Pompon: “Infected mosquitoes bite, but they don’t go to the vein, they can’t find it. The infection either changes the mosquito’s sensory organs or it is weaker.”

According to a study conducted in China, a derivative of vitamin A could attenuate the proliferation of a bacterium present in dengue fever in humans. This derivative, called isotretinoid, has already been tested on mice and the results have been conclusive.

For the MIGEVEC scientist, this may be a solution to counter the proliferation of dengue fever: “Why not, vitamin A is not toxic at too high a dose. We must do clinical trials on humans first.”

And precisely, tests are scheduled for this fall, in Malaysia.

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