Mixed-strain malaria infections affect disease's spread

Approximately 50 percent of the global population is considered at risk for contracting malaria. | File photo

Emory University scientists recently discovered that the competition between different strains of malaria parasites could affect how drug-resistant malaria spreads throughout humans.

When humans have co-infections of drug-sensitive as well as drug-resistant malaria strains, both of these strains suppress through competition. Typical anti-malarial therapy eliminates the drug-sensitive parasites from the co-infections. This may result in a competitive release of the resistant strains.

"We found that when hosts are co-infected with drug-resistant and drug-sensitive strains, both strains are competitively suppressed," Mary Bushman, lead author of the study and a Ph.D. candidate in Emory's Population Biology, Ecology and Evolution Graduate Program, said. "Anti-malarial therapy, by clearing drug-sensitive parasites from mixed infections, may result in competitive release of resistant strains."

The research, available in the Proceedings of the Royal Society B, suggests that new treatments need to be made available to resolve the spread of drug-resistant malaria.

"We're now down to our last treatment, artemisinin combination therapy, or ACT, and resistance to that recently emerged in Southeast Asia," Bushman said. "If ACT resistance continues to follow the same pattern, the world may soon be without reliable antimalarial drugs."

Approximately 50 percent of the global population is considered at risk for contracting malaria. This disease is complicated and challenging for researchers because it spreads through five different Plasmodium parasite species that infect humans through the bites of 30 to 40 different mosquito species, all of which behave differently.

"The epidemiology of malaria infection is different for different places and different conditions," Bushman said. "We hope that our work will spur development of new strategies to minimize resistance while maximizing the benefits of control measures.”

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