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Multi-drug resistant parasites threaten global efforts to control malaria, experts warn
The spread of multi-drug resistant malaria in south east Asia poses a "major threat" to efforts to eliminate the deadly disease, experts have warned.
Only half of patients in Cambodia, Thailand and Vietnam are being cured by front-line antimalarial drugs because of the “aggressive” spread of resistance in the malaria parasite, Plasmodium falciparum.
The disease is far less common in south east Asia than Africa, where more than 400,00 people died from the disease in 2017 - over 90 per cent of the total deaths worldwide.
But resistance in south east Asia is a concern because it could cross into Africa where it would have devastating effects, according to researchers from the UK and Thailand.
“[The] expansion and further spread of very difficult to treat, highly resistant P falciparum would cause a regional and potentially global health emergency,” the researchers warned in a study in the Lancet Infectious Diseases journal.
Since the millennium dramatic progress has been made in tackling malaria worldwide, but the fight against the disease is stalling. In 2017, the number of reported cases rose by 3 million to a total of 219 million globally, according to the World Health Organization.
This is largely because mosquitoes are increasingly resistant to the main insecticide used in bednets and sprays, as well as growing resistance to antimalarials among the malaria parasite.
P falciparum is the most deadly of the five parasites which cause malaria in humans after being transmitted by mosquitoes. It was responsible for nine in 10 malaria deaths and 200 million infections in 2017.
The Lancet published two studies tracking rising resistance to key antimalarial drugs in south east Asia.
A 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 said that efforts to eliminate malaria in the Greater Mekong region must be urgently accelerated.
And a genetic study of the multi-drug resistant parasite found that 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.
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