Netting mosquitoes to prevent malaria

A bed net, treated with insecticide, can reduce mortality rates of malaria by more than 50 percent in Africa. Click here for more information.

So far, Anopheles gambiae, the mosquito species that is responsible for transmitting malaria to humans in Africa, hasn't demonstrated any resistance to the insecticide used in the bed nets.

"It appears that the Anopheles gambiae population declines and doesn't recover," Walker said. "So the parasites that cause malaria shift into a different mosquito that feeds mainly on cattle. Since these mosquitoes don't bite people as often and cattle don't support the malaria infection, malaria transmission goes way down."

Walker and his colleagues also will be looking at the population structure of the malarial parasites to see how the population responds to decreasing mosquito populations.

"The parasites have a deep population structure—males outnumber females by about 8 to 1," Walker explained. "If there is a drop in total parasite numbers, it could be even harder for the parasites to mate."

According to Walker, this is important for two reasons. Malarial parasites are notorious for developing antibiotic resistance.

Restricting the population would restrict the gene flow, which would limit spread of the resistance. Walker's team will be using genetic markers to track the flow of genes. Second, when malaria transmission goes down, it tends to be the more virulent strains of the disease that survive.

"We don't want that to happen, so we'll be studying virulence factors to monitor it," Walker said.

The study also will examine how well people accept and use bed nets in their daily routines.

"I'm very excited to begin the project," he continued. "Bed nets are an inexpensive, easy-to-use method to control the disease. This research is international in scope and will help us help people, which is one of our land-grant principles."

Joseph Messina, MSU associate professor of geography, also is participating in the project.

This research is funded by the National Science Foundation and supported by the Michigan Agricultural Experiment Station. The Kenya Medical Research Institute and the U.S. Centers for Disease Control and Prevention are collaborators.

Contact: Ned Walker, microbiology and molecular genetics and entomology, (517) 355-6463, Ext. 1595; ; or Jamie DePolo, Michigan Agricultural Experiment Station, (609) 354-8403,