Artemisinin-resistant malaria ‘widespread’ in Southeast Asia
Researchers call for radical measures to prevent resistance to the most effective type of antimalarial agent spreading to the Indian subcontinent and beyond.
Source: CDC-Gathany/Phanie/Rex Features
Artemisinin resistance in Plasmodium falciparum is now prevalent across mainland Southeast Asia and represents a major threat to global malaria control, researchers report in The New England Journal of Medicine.
The study found that resistance to artemisinin — considered to be the most effective type of antimalarial agent — is firmly established in eastern Myanmar, western Cambodia, Thailand and southern Vietnam, and is emerging in southern Laos and north-eastern Cambodia. Artemisinin resistance was not detected in Africa at study sites in Kenya, Nigeria and the Democratic Republic of Congo.
Although artemisinin-based combination therapies remain highly efficacious in all regions studied, the researchers warn that the emergence of resistance across Southeast Asia “may well reverse the substantial recent gains in malaria control” and they call for “radical measures” to prevent resistance to artemisinin and its partner drugs further spreading to the Indian subcontinent and beyond.
“It may still be possible to prevent the spread of artemisinin-resistant malaria parasites across Asia and then to Africa by eliminating them, but that window of opportunity is closing fast,” says Nicholas White, senior author of the study and chairman of the Mahidol Oxford Tropical Medicine Research Unit (MORU) at Mahidol University, Bangkok, Thailand. “We will need to take more radical action and make this a global public health priority, without delay.”
More than half of the world’s population is at risk of malaria infection. Of the four parasite species that cause malaria, Plasmodium falciparum is one of the most common and the most deadly. There are more than 200 million cases of malaria every year, according to the World Health Organization (WHO). Although there has been a decline in mortality rates, which have fallen by 42% globally since 2000, there are still more than 600,000 deaths each year, most of them children in Africa.
The study, which was undertaken by the Tracking Resistance to Artemisinin Collaboration (TRAC), was an open-label trial in 1,241 adults and children with acute, uncomplicated falciparum malaria at 15 sites in 10 countries in Asia and Africa. Participants received artesunate followed by a standard three-day course of artemisinin-based combination therapy.
The response to treatment, as indicated by parasite clearance half-life, varied from 1.9 hours in the Democratic Republic of Congo to 7.0 hours at the Thailand–Cambodia border. Artemisinin resistance was strongly associated with a single point mutation in the kelch13 gene.
Treatment efficacy was uniformly high at all study sites, the researchers note; for instance, at Pailin in Cambodia, mean parasite clearance half-life was 6.1 hours, indicating resistance, yet the treatment failure rate at day 42 was just 2% after a six-day regimen. “Prolonged courses of treatment are one option for treating artemisinin-resistant malaria,” the authors write.
Citation: The Pharmaceutical Journal DOI: 10.1211/PJ.2014.20066045
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