Researchers have tested in Brazil with the release of mosquitoes-tiger-sterile drone to try to regulate the population. The study, published in mid-June in the journal Science and Roboticsreveals promising results.
Tens of thousands of mosquitoes released with the help of a drone is automated to fight against their own people, might seem counterintuitive. Yet this is what have tested scientific 2018 Carnaíba do Sertão, Brazil. The results were published in mid-June in the journal Science, and Robotics.
Each year, one million people die of a disease vector, a type of disease which constitutes 17% of infectious diseases in the world. Their main carrier ? The tiger mosquito. To eliminate it, the insecticides were more widely available, but their toxicity to many organisms and ecosystems has prompted the WHO to claim and promote new tracks. Among them, the sterilization, a method of genetic control, which has made its appearance in the early 2000s.
In march 2018, has thus tested the first release of male mosquitoes sterile by drone. Their goal : to fertilize a maximum of females, responsible for the transmission of diseases, in order to make their eggs non-viable and to bring down their population. In total, 50 400 insects have been released in a first experiment, after the first trials in the laboratory.
“It is to let go of in the nature of the male from a breeding and that have been sterilized by exposure to x-rays At the time of reproduction, they compete with wild males. But the females that will be mated with the individuals sterile will produce only eggs non-viable“, explains Jérémy Bouyer, who led the study, to Science and the Future.
Ten sterile males for a male wild
Previously, releases of mosquitoes sterile were made directly to the soil, limiting the ability of distribution of insects and asking a lot of humans in the work force. With this new method, the survival rates proved to be much better. Even if it requires a large number of mosquitoes breeding. “It is necessary to spread approximately ten sterile males for a male wild“in order to hope they are competitive, says the study director.
Crammed by the tens of thousands, the mosquitoes are in lethargy, into a tank maintained at a temperature of 10ºC. A cylinder with holes, placed under the tank recovers gradually from a party of mosquitoes and drop them on a “platform alarm clock“. Once on this platform, the insects, that are beginning to emerge, are propelled into the air. They will then wake up during a fall of 50 metres, the optimum height estimated for a good distribution of the sterile males, and high enough to allow a wake-up before reaching the ground. At high altitude, “they would be exposed to predators and we would have a lot of losses“says Jérémy Bouyer.
More than 50% of sterile eggs
To maximize the distribution of the male, the drone is automated. “When the experience of Carnaíba do Sertão, the uav had to cover an area of 20 hectares. Thanks to its embedded GPS system, it was programmed to precisely follow imaginary lines parallel to and spaced 80 metres. This spacing made it possible to obtain on the ground a density of mosquito homogenous given the speed of the drop. If the drone had moved away from these lines, the cylinder stop automatically turn to not let go of the males out of the box”, explains the researcher. And the conclusions are very satisfying. “With three releases, we have obtained more than 50% of sterile eggs. This is an excellent result” says the researcher.
Further experiments are planned in China, Thailand, Spain, or Singapore, and even in france, of which 58 departments have already been affected by invasions of mosquitoes-tigers increasingly important in recent years. In 2019, three cases of Zika was reported in France : three people infected by the mosquito are present on the territory.
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