Multidrug-Resistant Malaria Spreading in Southeast Asia -Study

By Kate Kelland

July 23, 2019

LONDON (Reuters) - Malaria parasites resistant to two key anti-malarial medicines are becoming more dominant in Vietnam, Laos and northern Thailand after spreading rapidly from Cambodia, scientists warned on Monday.

Researchers found in previous work that the Plasmodium falciparum co-lineage known as KEL1/PLA1 had evolved and spread across Cambodia between 2007 and 2013. This latest research, published in The Lancet Infectious Diseases journal, found it has crossed borders and tightened its grip.

Using genomic surveillance to track the spread of drug-resistant Plasmodium falciparum, the scientists found that KEL1/PLA1 has evolved and picked up new genetic mutations which may make it yet more resistant to drugs.

"We discovered (it) had spread aggressively, replacing local malaria parasites, and had become the dominant strain in Vietnam, Laos and northeastern Thailand," said Roberto Amato, who worked with a team from Britain's Wellcome Sanger Institute and Oxford University and Thailand's Mahidol University.

"The speed at which these resistant malaria parasites have spread in Southeast Asia is very worrying," said Olivo Miotto, who co-led the work.

The first-line treatment for malaria in many parts of Asia in the last decade has been a combination of dihydroartemisinin and piperaquine, also known as DHA-PPQ.

A separate paper in the same issue of the journal presents interim data from a multicenter randomized controlled trial comparing triple artemisinin-based combined therapies versus two-agent artemisinin-based combined therapies in areas with multidrug-resistant P falciparum malaria. Clinical efficacy rates of dihydroartemisinin-piperaquine at day 42 were 12.7% in northeastern Thailand, 38.2% in western Cambodia, 73.4% in northeastern Cambodia, and 47.1% in southwestern Vietnam.

"Compared with the results of our previous ... trial in 2011–13, the prevalence of molecular markers of artemisinin resistance ... and piperaquine resistance ... has increased substantially in the Greater Mekong subregion in the past decade," write the authors of the second report.

SOURCE:, and

Lancet Infectious Diseases 2019.