An aggressive strain of drug-resistant malaria that originated in Cambodia has rapidly spread into neighboring countries, causing high rates of treatment failure to first-line treatment and complicating efforts to eliminate the disease, according to two studies published yesterday in The Lancet Infectious Diseases.

One of the studies found that the KEL1/PLA1 strain of Plasmodium falciparum, the parasite that causes malaria, now accounts for more than 80% of the malaria parasites in northeastern Thailand and Vietnam, and has acquired new genetic mutations that have enhanced its fitness and ability to resist treatment. The strain is resistant to dihydroartemisinin-piperaquine, a form of artemisinin-based combination therapy (ACT) that has been the first-line treatment for malaria in Cambodia for more than a decade, and was more recently adopted as the preferred treatment in Thailand and Vietnam.

The other study found that the average failure rate for dihydroartemisinin-piperaquine treatment in Cambodia, Vietnam, and Thailand is now 50%, which suggests a new front-line option is needed to battle the mosquito-borne disease in those countries.

A 2018 study in The Lancet reported that KEL1/PLA1 parasites first appeared in western Cambodia in 2008, shortly after dihydroartemisinin-piperaquine was introduced, and by 2013 had migrated to northern Cambodia and Laos. By 2015 and 2016, they had been identified in Thailand and Vietnam. Resistance to the treatment was first reported in Cambodia in 2013.

“These worrying findings indicate that the problem of multidrug resistance in P falciparum has substantially worsened in southeast Asia since 2015,” Professor Olivo Miotto, PhD, of the Wellcome Sanger Institute and University of Oxford, who was involved in both studies, said in a Lancet press release.

Credit CDC

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