Mosquitoes in South America are evolving to evade insecticides, a troubling implication for the spread of malaria in that part of the world.
The Anopheles darlingi mosquito is a major vector of malaria in the Americas, which has seen meaningful progress in combating the parasitic disease: In thepast eight years Paraguay, Argentina, El Salvador, Belize, and Suriname were all certified as malaria free by the World Health Organization (WHO). Still, according to the WHO’s Pan American Health Organization, 136 people in the Americas died of malaria in 2024.
Astudy published last month in the journal Science shows this recent progress is under threat because of changes to the cytochrome p450 genes in Anopheles darlingi. Researchers suspect this adaptation allows this species of mosquito to metabolize toxic substances faster, compromising the usefulness of pesticides for malaria mitigation in countries like Brazil, Colombia, and Peru, where several of the study’s authors are based.
Mosquitoesevolve fast
Mosquitoes are highly adaptable owing to their sizable population, which eclipses that of humans or other large animals, explained lead author Jacob Tennessen, PhD, an evolutionary biologist specializing in parasitic diseases at the Harvard TH Chan School of Public Health.
Large populations lead to greater genetic diversity. At the same time, mosquitoes reproduce rapidly, with potentially 10 or more generations per year. These factors mean that natural selection can force swift evolutionary changes, which is how insecticide resistance can form over a relatively short period.
Insecticides critical for malaria mitigation
Tennessen said he hopes this research will lead to more work on best practices for pesticide management in the agriculture industry, such as using chemicals that are less likely to drive evolutionary changes in mosquitoes. He noted that insecticide resistance in mosquitoes is a growing challenge that contributes to the ongoing spread of malaria in Africa, which sees 95% of malaria cases worldwide, according to WHO data.
It’s really important to, even after malaria becomes rare in a place, to keep pushing to make it completely gone there.
Preventing insecticide resistance is not only important for public health in South America, but also globally in the battle against malaria.
“It’s really important to, even after malaria becomes rare in a place, to keep pushing to make it completely gone there. Because otherwise it could evolve resistance, and then that resistance could spread to the rest of the world,” he said.
