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Thursday, November 19, 2009

Spread of artemisinin resistance may hinder efforts to control malaria

As resistance to the antimalarial drug artemisinin increases, efforts to control malaria may be threatened, according to experts who spoke at the American Society of Tropical Medicine and Hygiene's 58th Annual Meeting in Washington, D.C.

Currently, the bulk of artemisinin resistance has been observed near the border between Cambodia and Thailand. But experts are warning that it could soon spread throughout Southeast Asia, hampering malaria control efforts in the region and elsewhere.

"Artemisinin combination therapies are the most rapidly and reliably effective treatments for malaria caused by the Plasmodium falciparum parasite, which is responsible for the vast majority of malaria-related illnesses and deaths," Pascal Ringwald, MD, director of antimalarial drug resistance surveillance at WHO, said. "The loss of artemisinin derivatives to resistance could have a devastating effect on health in tropical countries and would threaten current global efforts to eliminate malaria."

Ringwald said WHO officials first noticed evidence of artemisinin resistance in Cambodia and Thailand after receiving reports about increases in clearance times in patients with malaria treated with artemisinin combination therapies. "These drugs are designed to kill the parasites within 24 to 48 hours, but we are finding that it sometimes takes four or five days to kill them," Ringwald said. "In some studies, half of the parasites are not killed within 72 hours after the beginning of treatment, which indicates a growing resistance problem."

Ringwald added that artemisinin resistance is particularly problematic because there are few antimalarial drugs currently in development that could, if necessary, replace artemisinin in terms of effectiveness.

However, Ringwald also stressed that although artemisinin resistance is a growing concern and health officials are monitoring of the situation, the "vast majority" of patients with malaria throughout the world are still being treated and cured with artemisinin-based therapies.

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