Bed nets treated with insecticide aren’t enough to stop a new “super mosquito”—the result of interbreeding by two malaria mosquito species in the West African country of Mali.
Anopheles gambiae, a major malaria vector, is interbreeding with isolated pockets of another malaria mosquito, A. coluzzii. Entomologists initially considered them as the “M and S forms” of Anopheles gambiae—but now recognize them as separate species.
“It’s ‘super’ with respect to its ability to survive exposure to the insecticides on treated bed nets,” says medical entomologist Gregory Lanzaro, professor in the pathology, microbiology and immunology department at University of California, Davis.
Published in the Proceedings of the National Academy of Sciences, the research “provides convincing evidence indicating that a man-made change in the environment—the introduction of insecticides—has altered the evolutionary relationship between two species, in this case a breakdown in the reproductive isolation that separates them,” Lanzaro says.
“What we provide in this new paper is an example of one unusual mechanism that has promoted the rapid evolution of insecticide resistance in one of the major malaria mosquito species.”
The insecticide resistance came as no surprise, Lanzaro says.
“Growing resistance has been observed for some time. Recently it has reached a level at some localities in Africa where it is resulting in the failure of the nets to provide meaningful control, and it is my opinion that this will increase.”
Insecticide-treated nets can be credited with saving many thousands, probably tens of thousands of lives, in Mali alone, Lanzaro says.
The World Health Organization’s World Malaria Report indicates that deaths from malaria worldwide have decreased by 47 percent since 2000. Much of that is attributed to the insecticide-treated bed nets.
However, it was just a matter of time for insecticide resistance to emerge. Now there’s “an urgent need to develop new and effective malaria vector control strategies,” Lanzaro says.
A number of new strategies are in development, including new insecticides, biological agents—including mosquito-killing bacteria and fungi—and genetic manipulation of mosquitoes aimed at either killing them or altering their ability to transmit the malaria parasite.
Other researchers from UC Davis and from the University of Bamako in Mali are coauthors of the study. The National Institutes of Health funded the research.
Source: UC Davis