two possible routes against dengue

Modifying the physiological constitution of mosquitoes that are vectors of diseases to fight against their transmission: for the past twenty years, two strategies have been studied, from bench-top to trials in the wilderness. “ Until now, insecticides have been the main control tool. But it is clear that we have reached the limits of their use: on the one hand because these toxic molecules end up in the environment and food chains, on the other hand because mosquitoes quickly develop resistance ”, explains Frédéric Simard, research director at the French Development Research Institute (IRD). This specialist therefore welcomes these “Two new techniques” of mosquito control.

The first is to release mosquitoes made carriers of a bacteria called Wolbachia, naturally present in two out of three insect species, and which has the effect of either preventing them from transmitting the virus of certain pathologies, or of suppressing mosquito populations. Although the exact mechanism of host-parasite interactions is not fully understood at the molecular level, several trials of this technique have been conducted or are underway around the world.

The other method consists of intervening directly in the mosquito genome to modify it, and give it new properties. Scientists at the British-American company Oxitec, for example, managed to get males of the species to wear Aedes aegypti (which can transmit various viruses to humans, including dengue) a “self-limiting” gene: when these, once released, fertilize females, the female descendants perish. Young males survive and, through Mendelian genetics, transmit this same gene to half of their male offspring.

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And like only females Ae. aegypti bite humans, this method, which limits their proliferation, also reduces the incidence of the diseases they carry. The only problem: the transmission of the “self-limiting” gene also diminishes over time, forcing new releases of modified males.

Critiques

Oxitec, which boasts of being the world leader in the production of genetically modified insects, has already carried out several experiments, notably in Brazil in 2014, with a more primitive version of its mosquitoes. This trial was initially criticized in particular for fear that scientists would lose control of the genetic alteration carried out. In 2021 however, with its second generation of transgenic mosquitoes, the company landed a big contract to launch its Diptera squads in Florida, but not without resistance from the population.

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