Government health workers screen people for diseases like malaria at a weekly market in Orchha in central India's Chhattisgarh State in November 2022. Photo / AP
Government health workers screen people for diseases like malaria at a weekly market in Orchha in central India's Chhattisgarh State in November 2022. Photo / AP
The rapid emergence of a new drug-resistant malaria parasite in Laos has triggered an “unusual” jump in cases and sparked concern among experts.
Between 2019 and 2020, malaria cases in Attapeu, a region in southern Laos, surged from 378 to 868 – a 130 per cent increase in an areawhere infections have consistently been falling.
Across Southeast Asia, several countries are close to wiping out malaria, and other regions in Laos saw cases fall by 65 per cent over the same period.
“This peak in Attapeu was very unusual,” said Prof Olivo Miotto, head of the GenRe-Mekong Genetic Surveillance project at the Mahidol-Oxford Tropical Medicine Research Unit in Bangkok.
“The concern was not so much the absolute number, it was that the trend had reversed – because that could be an indication that things are going wrong.”
But now, scientists tracking the outbreak have linked it to the spread of a drug-resistant malaria parasite, which gained an advantage after the antimalarials used in neighbouring countries were changed.
Experts compared the shift to the emergence of omicron, which replaced delta as the most widespread Covid-19 variant in late 2021.
The findings, published in Lancet Infectious Diseases, highlight the unintended consequences that changes to malaria policies in one country can have elsewhere. In this case, using a new combination of antimalarials wiped out one strain but gave another space to spread.
“As one strain waned, other resistant strains readily took its place, causing a resurgence of the disease,” said Prof Miotto, co-author of the report.
The research – which used genomic data from 249 blood samples in Attapeu – also demonstrates the challenges involved in the push to malaria elimination, and the need for heightened surveillance to rapidly pick up troubling new mutations in malaria parasites.
Since the 1950s, parasites resistant to antimalarial drugs have consistently emerged in the Greater Mekong subregion.
Scientists are not entirely sure why, but one theory is the “Last Man Standing” model. This suggests that as you put intense pressure on malaria parasites, they become more resistant as they struggle to survive, the last one becoming the toughest of all.
A surgeon prepares a malaria test for 23-year-old Tigrayan refugee Hareg from Mekele, Ethiopia in November 2022. Photo / AP
This logic holds in the Laos outbreak, said Dr Miotto.
“I think what’s happening in this region is [that] the parasites have become more and more apt at tolerating [drug-resistant] mutations – even though such mutations may hurt them in other ways.
“That’s why, even though there’s very few cases in the Greater Mekong sub-region, they’re of great concern – because the parasites that circulate have repeatedly developed resistance to all the antimalarials we know of. And that will likely continue until they’re completely eliminated.”
A global problem
Dr Miotto added that the outbreak in Laos highlights are two potential concerns for Africa. First, that these resistant strains could leapfrog to the continent – where the impact would be devastating, as malaria is far more prevalent.
“Ultimately, the drive to eliminate malaria [in southeast Asia] is primarily to protect African countries … it would be a disaster if drug resistance became more widespread there,” he said.
But it also highlights potential pitfalls for countries, such as Uganda and Rwanda, where cases are falling substantially – a trend experts hope will be accelerated as new tools to combat malaria, including vaccines, become available.
“As the number of cases in Africa decreases, more and more regions will develop the right conditions for antimalarial resistance to occur, and for the same sort of epidemiological phenomena that we’re seeing in Southeast Asia to emerge,” said Dr Miotto.
