Last spring, the global health community got some alarming news about its last, best treatment for malaria. The artemisinin-based drugs were losing their potency at two different places in Southeast Asia: in western Cambodia and along the border between Thailand and Myanmar.
Health workers feared that it was only a matter of time before the resistant malaria would show up elsewhere.
Now there are signs that artemisinin-resistant malaria is cropping up in Vietnam and central Myanmar, researchers reported Tuesday at the annual meeting of the American Society of Tropical Medicine and Hygiene in Atlanta.
"Showing that resistance is emerging outside of western Cambodia is a game changer," says Dr. Rick Fairhurst, an infectious disease specialist from the National Institute of Allergy and Infectious Diseases, who co-chaired the study. "There are other places, up and coming, that we'll have to be deal with now."
For the past year and a half, Fairhurst and a team of doctors from Oxford University have closely monitored 883 malaria patients at 12 locations in Cambodia, Thailand, Myanmar, Bangladesh, Vietnam and Laos. The researchers have been measuring how quickly the Plasmodium parasite leaves patients' blood after they're given artemisinin.
Patients in the drug-resistant hot spots of western Cambodia took the longest time to recover from malaria infections, as researchers expected. But at clinics more than 300 miles away in Vietnam, the results were mixed. Some patients wiped out the infections fast, but others were quite slow to recover. The team saw the same split at clinics in central Myanmar.
Some researchers at the meeting were hesitant to label this slow clearance of the parasite drug resistance because several factors can influence how fast the drug works, including a patient's age and the malaria species. Plus, artemisinin still kills the parasite, eventually. It just takes longer.
This is good news, Fairhurst says, because it means doctors can still use the drug to treat malaria in these locations. They probably just have to be extra careful, and perhaps add another medication to make sure they wipe out all forms of the parasite.
"We may need to get more serious about using a second drug to kill the gametocytes [one stage of the parasite]," he tells Shots. "The guidelines say to do this, but it is not in widespread use."
Although the study is still ongoing, the team hasn't found any signs of sluggish recovery in Laos or Bangladesh With careful surveillance and mapping of malaria infections, Fairhurst says he's hopeful that health workers will be able to stay ahead of artemisinin resistance before it spreads to other parts of Southeast Asia.