Drug-resistant malaria strain may threaten millions

Malaria is becoming resistant to the most powerful drugs available in Southeast Asia, as the World Health Organization races to stop the spread of the strain that could be "disastrous" for global malaria control.

Treatments derived from artemisinin, the basis of the most effective anti-malaria drugs, took almost twice as long to clear the parasites that cause the disease in patients in western Cambodia as in patients in northwestern Thailand, according to a study published in the current New England Journal of Medicine.

The delay in parasite clearance times shows the drugs are losing their power against the disease in Cambodia, the study said. The failure of artemisinin-based treatments would be "disastrous" for global efforts aimed at curbing the death and disease wrought by the malady, said Arjen Dondorp, who led the study at the Mahidol Oxford Research Unit in Bangkok.

"There is no question that this is resistance to artemisinin," Carlos Campbell, a malaria expert with the Seattle-based Program for Appropriate Technology in Health, or PATH, wrote in an editorial accompanying the study. "History warns us that it will intensify and spread unless containment steps are taken."

Scientists have known for decades that Pailin, near Cambodia's border with Thailand, is a breeding ground for drug-resistant malaria. Chloroquine and another drug, Fansidar, started to fail there in the 1950s and 1960s, before becoming ineffective elsewhere, according to the study. The WHO, with $23 million from the Bill & Melinda Gates Foundation, is coordinating efforts to prevent artemisinin-resistant malaria from spreading to Africa, which has 90 percent of the world's cases of the disease.

Widespread artemisinin resistance "would cause millions of deaths, without exaggeration," Dondorp said in an interview in January.

Malaria strikes about 250 million people each year and kills more than 880,000, mostly children under 5. It's the world's third-deadliest infectious disease, behind AIDS, which results in about 2 million deaths each year, and tuberculosis, which kills 1.6 million people annually, the Geneva-based WHO said.

Malaria is caused by a tiny parasite called Plasmodium, carried in the saliva of female mosquitoes. When an infected insect bites a person, the bugs travel to the liver, multiply and enter the bloodstream. There they invade red cells, leading to fever, chills, nausea and diarrhea. Unchecked, they cause red cells to stick to the walls of capillaries, slowing blood flow. Sufferers can die from organ failure without treatment.