Mosquito bites are responsible for the dispersal of many human diseases. To reduce the number, American researchers have found a surprisingly simple solution: to make these insects lose the taste of blood by cutting their appetite.
Mosquitoes are formidable hunters, able to detect the presence of humans by the CO2 they expire at distances up to 50 meters. Now, the danger represented by these insects greatly exceeds the drops of blood they subtilize us.
Mosquitoes carry diseases that kill millions of people every year. Malaria, for example, has been transmitted to 219 million people in 2017, of whom 435,000 have died, according to the World Health Organization.
Several researchers are trying to find a way to eliminate mosquitoes carrying dangerous diseases with methods ranging from new insecticides to the elimination of certain species by genetic modifications.
However, these methods also have their own set of problems, pushing some scientists to focus on less destructive tactics. For US researchers (New Window) at Rockefeller University, these methods may be based on appetite control, a method that, in their most recent study, has proven particularly effective.
In mosquitoes, females bite animals only when they have to lay eggs. Outside these periods, they get their energy from other sources such as nectar. Once they get their blood meal, they lose interest in their prey for several days, even if it comes to pass one directly within their reach.
Several studies have shown that this behavior is regulated by a neuropeptide, a molecule that allows the transfer and regulation of information between neurons.
One of these molecules, the neuropeptide Y, is found in a large number of animal species, including mosquitoes and humans, and plays several roles in the nervous system, including regulating food intake.
However, there are already several “hunger suppressant” drugs marketed by various pharmaceutical companies and whose mechanism of action targets neuropeptide Y in humans.
By introducing these appetite suppressants into the water of Aedes aegypti mosquito colonies , responsible for the spread of several human diseases, Rockefeller University researchers quickly found that these insects lost interest in humans, as if they were had already had their blood meal.
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Although this first observation was interesting, it was also necessary to understand the exact mechanism of this reaction.
Humans have only four variants of neuropeptides Y, but Aedes aegypti has 49. To target only these insects and avoid spreading a drug that can also act on humans, it was crucial to know how it works.
By observing which variant was affected by the drug, the team identified a protein, NPYLR7, which was found to be the sole cause of the appetite suppressant observed in mosquitoes.
With this information, the researchers then went in search of a molecule able to act exclusively on this neuropeptide without having any effect on those found in humans.
Finally, they identified six of these molecules. Although spreading these products today would stop mosquito bites for a few days, there are still many problems to overcome before such distribution is considered.
For example, it is very important to ensure that only mosquitoes come in contact with the product, and that it does not affect other pollinating insects. In addition, the researchers noticed that only the high doses of these molecules had an effect; this condition would make this type of intervention much too expensive to be useful at the moment.
However, the method has the advantage of not leading to the large-scale death of insects, as would be the case when using insecticides, thus avoiding unintended consequences for the rest of the food chain.