The strains are currently contained to parts of southeast Asia where the disease has greatly declined over the last decade. But they could be devastating if they were to reach more malaria-ridden regions such as sub-Saharan Africa, experts say.
Here are five key findings from the reports.
What exactly did the studies find?
Two studies published in the Lancet journal of infectious diseases last week found that resistance to the most common form of anti-malarial drugs has spread and gotten worse since 2013. To treat malaria cases, health workers primarily use a combination of dihydroartemisinin and piperaquine, or DHA-PPQ. The medication is given in pill form that can be taken by mouth.
According to the new research, in the regions tested, this treatment failed to cure the disease at an overall rate of 50 percent — or 13 percent in northeastern Thailand, 38 percent in western Cambodia, 73 percent in northeastern Cambodia and 47 percent in southwestern Vietnam.
Does that mean there are forms of malaria that can’t be cured?
Not exactly. There are several drug combinations out there that could still treat the resistant strains. But the treatments themselves can breed more resistance.
“In general, using treatments to kill microorganisms creates a selective advantage for resistance to emerge and spread,” said Will Hamilton, a medical student at the University of Cambridge and an author on one of the studies. “This is evolution by natural selection in action.” He compared the rising phenomenon of bacteria developing resistances to antibiotics.
And there are only a limited number of alternative treatments.
“The problem with malaria is that the treatment options are very limited,” Dondorp said. “Once you can’t treat the infections very well, malaria will increase again, and once the number increases, the number of deaths will increase.”
Why is this happening in southeast Asia?
Southeast Asia has historically been a breeding ground for the development of resistant malaria strains. Scientists are not completely sure why, but suspect it’s partly to do with the fact that antimalarial drugs are widely and heavily used there, Hamilton said. The pervasiveness of the medication puts pressure on the strains to adapt and find ways to develop resistances.
Another reason, Dondorp said, could be how malarial drugs are taken in the region. Patients with malaria may take weaker medication, or stop taking pills once they feel better instead of finishing out the treatment, making the parasites more resistant to the drugs.
Lastly, southeast Asian countries have a relatively low transmission rate, meaning resistant strains run up against less competition from more dominant nonresistant strains.
What would happen if this resistance were to spread?
It would be bad. A major concern is that the strains will spread to sub-Saharan Africa, where malaria is most common and logistically hard to treat.
There is precedent for this. In the 1960s, a strain of malaria that developed in southeast Asia became resistant to the then-commonly-used drug chloroquine and eventually spread to sub-Saharan Africa. The lack of alternative medications led to the amount of malaria-related deaths doubling in the 1980s.
Scientists fear history could repeat itself.
“The spread of these resistant parasites to other regions like Africa is highly possible and a real concern,” said Didier Ménard, the head of the Malaria Genetic and Resistance Group at the Institut Pasteur Paris and one of the reviewers of the studies.
What can be done in the meantime?
Ultimately, scientists say, the only way to completely eradicate these resistant strains is to eradicate the disease itself in the region.
Such efforts have taken place around the world since 1955, when the World Health Organization created the Malaria Eradication Problem. Since then, dozens of countries have been declared as malaria free, but only two of them, the Maldives and Sri Lanka, are in southeast Asia.
“We really have a great sense of urgency to eliminate malaria from the region,” said Dondorp, “otherwise we will never be able to eliminate malaria. It will come back and spread to other countries.”