Malaria: Artemisinin resistance continues developing in western Cambodia

Jul 30 2009

Artemisinin, the "basis of the most effective" malaria treatment recommended by the WHO, took nearly twice as long to clear malaria parasites in patients in western Cambodia than it did in patients in northwestern Thailand, according to a New England Journal of Medicine study, which shows the "drugs are losing their power against the disease in Cambodia," Bloomberg reports (Bennett, 7/30).

For the study, researchers at the Wellcome Trust-Mahidol University Oxford Tropical Medicine Research Program "compared the effects of artemisinin drugs in 40 malaria patients in western Cambodia and 40 patients in northwestern Thailand. On average, the patients in Thailand were clear of malaria parasites within 48 hours, compared to 84 hours for the Cambodian patients," according to HealthDay News/U.S. News & World Report (7/29).

"We do not see 100 percent resistance, but the parasite is much less susceptible to artemisinin than we are used to. If used in combination with other drugs we can still cure malaria but it takes a few days longer," Arjen Dondorp, the leader of the study, said, the Telegraph reports (Leach, 7/30).

For decades, scientists have known that the area near Cambodia’s border with Thailand, "is a breeding ground for drug-resistant malaria," according to Nature News (Sanderson, 7/29). Chloroquine "started to fail there in the 1950s and 1960s, before becoming ineffective elsewhere, according to the study. The WHO ... is coordinating efforts to prevent artemisinin-resistant malaria from spreading to Africa, which has 90 percent of the world’s cases of the disease," Bloomberg writes (7/30). In an accompanying NEJM editorial, PATH's Carlos Campbell, who was not involved the study, writes "that the results leave no question that there is artemisinin resistance in western Cambodia," according to ScienceNow (Vogel, 7/29).

In a separate study published in the same issue of NEJM, scientists used "chloroquine to protect people while gradually exposing them to malaria parasites and letting immunity develop," according to the AP/Washington Post. "The results were astounding: Everyone in the vaccine group acquired immunity to malaria; everyone in a non-vaccinated comparison group did not, and developed malaria when exposed to the parasites later," the AP/Washington Post writes.

"The study was done in a lab at Radboud University in Nijmegen, the Netherlands, and was funded by two foundations and a French government grant," according to the news service. While, a "vaccine that uses modified live parasites just entered human testing," this particular study "was only a small proof-of-principle test, and its approach is not practical on a large scale similar," according to AP/Washington Post (Marchione, 7/30).