Multi-drug resistant parasites threaten global efforts to control malaria, experts warn

Only half of patients with malaria in south east Asian countries are being cured because multi-drug resistant forms of the parasite are now so widespread, researchers have found.

According to two studies published in the Lancet Infectious Diseases journal on Tuesday, rising resistance to antimalarial drugs in the Plasmodium falciparum parasite could stall efforts to eliminate the disease and present a "major threat" to efforts to control the disease.

The P falciparum is the most deadly of the five parasites transmitted by mosquitoes and lead to malaria in humans. It is responsible for nine in 10 malaria deaths worldwide and 200 million of the 217 million malaria infections reported in 2017.

Malaria is not as prevalent in south east Asia as in Africa, but the rise of resistance is a concern because it could spread internationally.

The clinical trial looked at 140 patients who received malaria treatment in Cambodia, Thailand and Vietnam and found that around half were not cured by first-line antimalarial drugs. The researchers warned that efforts to eliminate malaria in the Greater Mekong region must be urgently accelerated.

“[The] expansion and further spread of very difficult to treat, highly resistant P falciparum would cause a regional and potentially global health emergency,” the authors wrote.

According to the linked genetic study of the multi-drug resistant parasite, the mutation only emerged in Cambodia in 2008 but it has spread rapidly, especially since 2015.

Between 2016 and 2018, more than 80 per cent of parasites in circulation in northeast Thailand and Vietnam carried the resistant strain.

“One thing that was particularly worrying is how fast the mutations have spread from Cambodia to neighbouring countries,” Dr Roberto Amato, joint first author from the Wellcome Sanger Institute, told The Telegraph.

“We discovered that the multi-drug resistant malaria strain had spread aggressively, replacing local malaria parasites, and had become the dominant strain in Vietnam, Laos and north eastern Thailand,” he said.

Both the antimalarial drug artemisinin and its widely used partner drug piperaquine failed to kill the malaria parasite, which also showed signs of resistance to new powerful front-line drug combinations.

The reports call for continued tracking of drug resistance across the region and recommended new front-line antimalarial drug combinations.

“The spread of drug-resistant strains... provides a warning signal,” said Dr Michael Chew, infection and immunobiology portfolio manager at the Wellcome Trust. “It serves as a reminder that we must not show complacency with the response to malaria.

“It also shows we have the tools to effectively track drug resistance across borders, which can be used to inform co-ordinated elimination and control efforts,” he said.

Writing a comment piece in The Lancet, Dr Didier Ménard from the Institut Pasteur in France, said: “These two studies highlight the urgent need to adopt new and effective treatments.

“These findings also demonstrate the advantages of implementing a regional strategy rather than country-specific programmes to address [parasite] population movements,” he added.

Protect yourself and your family by learning more about Global Health Security