This is an encouraging discovery, as summer approaches. Scientists at the Hebrew University of Jerusalem in Israel say they have developed a new type of repellent that reduces the risk of mosquito bites by at least 80 percent, according to a study published in April in the journal PNAS Nexus. The announcement holds promise as malaria and other mosquito-borne diseases, such as dengue fever, affect millions of people worldwide, according to the World Health Organization.
The new formula offers "mechanical protection" against mosquito bites, but also acts as a "chemical camouflage," said Dr. Jonathan Bohbot, a researcher at the Hebrew University, quoted by Euronews. Unlike a repellent such as lemongrass, which has an odor that keeps mosquitoes at bay, this new product forms a "barrier" that would block body odor and limit the risk of bites. In addition, and unlike the former, it would be effective sustainably, say the authors of the study.
The risk of bites reduces by 80%
The formula developed is a mixture of two natural elements: cellulose, the main constituent of the wall of many plants, and indole, an aromatic substance present in some flowers - which also acts as a mosquito repellent.
Several experiments have been conducted to test its effectiveness. In the first, a scientist slipped his hand into a cage housing fifteen mosquitoes. The authors of the study found that applying a layer of cellulose nanocrystals to the exposed part of the skin reduced the risk of bites by 80%.
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The method showed even better results when combining these nanocrystals with indole: it resulted in a 99.4% reduction in egg-laying after exposure to blood in the laboratory. Used together, these two natural elements form a "perfect, long-range, long-lasting personal protection system," Bohbot said. Scientists have also highlighted the fact that cellulose retains ammonium hydroxide, one of the volatile organic compounds released by the skin, which attracts mosquitoes.
"Still a lot of steps to take"
While further experiments are needed to confirm the effectiveness of the formula, the authors conclude that cellulose's properties make it "ideal" for the development of a new generation of mosquito repellent – and hope that this new type of repellent will be available on the market as early as next year.
"It's their role to be enthusiastic, but I will be more measured," says entomologist Grégory L'Ambert, while acknowledging that this discovery is "good news". "These results may be promising, but there are still a lot of steps to take," he adds. Researchers will first need to ensure that the recipe is "safe", that is, that it is safe for humans.
It will also be necessary to test its effectiveness in real conditions: will the results be the same with "wild" mosquitoes, and against humans on the move? "There are many things that work well in the laboratory but are actually not so effective," observes the specialist, who also highlights the ability of mosquitoes to adapt to new methods. "In Africa, a species of mosquito that only bitten at night started biting earlier, from the moment people started using mosquito nets," he says, before concluding: "We have to be careful, but that doesn't mean we shouldn't pay attention to it."