Humans have been fighting against maringouins for a long time, and sometimes even tries to eliminate them. For the moment, with limited success: these insects are present on all continents, with the exception of Antarctica and some islands.
But research teams around the world are developing ever more precise methods that are changing the situation.
Fight the mosquito by … the mosquito
Steve Whyard, a biology professor at the University of Manitoba, perfectly proven by eliminating a kind of meat fly from North America. The idea is simple: sterilize male insects in the chosen species in the laboratory, then release them in the wild.
In some species of mosquitoes (including the common mosquito, well present in Quebec), the female generally only mates once in her life. If it mate with a sterile male, it will not produce any baby.
“The attraction of technique is that it is specific to a species, since mosquitoes only mate with their fellows. And it is a local control technology, because mosquitoes do not travel very far. ”
— Steve Whyard, biologiste
In theory, it could therefore be used in cities by regularly releasing swarms of transgenic mosquitoes. This would replace pesticides that many municipalities are already spreading to combat harmful insects, and can even be more efficient.
However, the method is not designed to eliminate a species for good, but other researchers develop much more aggressive. Because elsewhere in the world, mosquitoes represent more than just a nuisance. Because of the diseases they transmit like malaria or dengue, mosquitoes are responsible for more than 725,000 deaths each year, most of them in sub -Saharan Africa.
Challenge genetics
One of these approaches is to develop transgenic mosquitoes with disadvantageous features that they will transmit to their descendants, like a gene to make their children female sterile.
Previously, the problem of these techniques was that the mosquitoes had only 50 % chance of transmitting the modified gene to their descendants. The modification therefore tended to disappear by itself over the generations. But recent advances in genetic manipulations make it possible to artificially amplify the transmission of the gene, which leads mosquitoes to transmit it to 99 % of their descendants.
Result: “We can free a very small number of mosquitoes and they will do the work themselves, spreading this modification on a large scale,” says Federica Bernardini, researcher who studies this technique for the research consortium Target Malaria.
In laboratory tests in 2018, the introduction of a gene affecting the fertility of female mosquitoes, combined with this new technology, led a captive population of mosquitoes to extinction after only eight generations.
Eradicate or not?
Other techniques are still developing to combat insects carrying illness. Last March, the biology professor at Notre-Dame Lee Haines University demonstrated that a drug used to treat rare diseases also had the effect of making our blood toxic for insects that drink it. The mosquitoes died in less than a day. “It’s very powerful,” she says.
These technologies, combined with classic traps and insecticides, could soon make us able to completely eliminate certain species, according to Steve Whyard and Federica Bernardini.
It is not necessarily the objective of scientists who fight malaria, notice. “We don’t need to eradicate a species to eliminate malaria,” explains Talya Hackett, a researcher at Target Malaria. Just reduce the mosquito population enough to break the transmission cycle. ”
However, if they had the option of eradicating mosquito -bearing mosquitoes with a snap of the fingers, almost all the researchers interviewed would do it. “Without hesitation,” said Frédéric Simard.
Not a big role in ecosystems
Now if they were eliminated, what repercussions would it have on their ecosystems?
Talya Hackett has been studying the role for theAnapheles gambiaethe main mosquito with Malaria, in a Ghana ecosystem. With her team, she observed which insects landed on the flowers of the region, and analyzed the contents of the stomach and the boxes of birds, geckos or spiders.
Its results are preliminary, but they suggest that the disappearance of theAnapheles gambiae would not have a big impact on its environment. “They are not particularly effective pollinators,” she explains. And they seem to form only 1 % of the diet of animals that eat them.
“What they bring is misery and suffering,” according to Lee hatred.
And here?
The question is more delicate when asked about mosquitoes that bite us without transmitting diseases, like most of those present in Quebec.
Here either, they probably do not play an irreplaceable role in the ecosystem. “They serve as foods for insectivores, but their role is not very specific,” explains Frédéric Simard. There is no insectivore that depends on the mosquitoes. ”
One of the only places where their disappearance could have a notorious impact, according to him, is northern Canada. Mosquitoes are present in such large numbers during the summer that they bring animals such as caribou to choose precise paths to avoid them, or sometimes even swimming in the middle of the lake until they are drowned.
For Steve Whyard, the need to take into account the mental health of the population justifies to eliminate mosquitoes in town, but not to disturb this kind of wild ecosystem.
And thanks to the nuisance they cause, wild mosquitoes even have the effect of protecting certain natural areas, discouraging populations to settle there. “They are kinds of guards, in a way,” says Lee Haines.
