A crucial malaria drug that lost its punch in most countries because of germ resistance now appears to be highly effective again in one African nation — a startling shift with implications for other tough bugs.
It appears to be the first time a drug widely used against a killer disease has regained effectiveness after a break in use.
“We didn’t expect to see this,” said researcher Dr. Christopher Plowe of the University of Maryland School of Medicine. “I’m not aware of any case where a drug wasn’t working clinically and was withdrawn and now is 100 percent effective again.”
The drug, chloroquine, was for many years the standard for treating malaria because it is very cheap, effective and safe. But in 1993, doctors stopped using it in the African nation of Malawi, because it was no longer effective in fighting most malaria cases.
However, in recent years, researchers saw signs of genetic shifts in malaria that suggested it might again be vulnerable to chloroquine.
University of Maryland researchers tested it in 105 malaria-infected children at a clinic in central Malawi. An astounding 99 percent of them were cured, far better than the results of two drugs tested on another group of children.
The findings, reported in Thursday’s issue of the New England Journal of Medicine, show that other African nations should stop using chloroquine, as the World Health Organization recommends. Once evidence shows the drug works again, experts say, those countries could resume using it, but in combination with other antimalarial drugs. Research shows infectious agents are far less likely to develop resistance when hit by a few drugs at once.
Malaria remains one of the world’s deadliest diseases. It kills about 1 million children a year in poor countries with warm, damp climates ideal for the mosquitoes that transmit the malaria parasite.
Experts at the U.S. Centers for Disease Control and Prevention, Johns Hopkins University School of Medicine and elsewhere said they knew of no case where a drug against a parasite regained effectiveness, although it has happened with a few drugs against other organisms.
Those include the herpes simplex virus and a bacteria that causes pneumonia and blood infections, said Dr. Melvin Weinstein, chief of infectious diseases at Robert Wood Johnson Medical School.
“I think it’s extraordinary because it’s unexpected,” Weinstein said of the chloroquine reversal.
Experts said these results could help doctors fighting drug-resistant bacteria and other germs.
Resistance occurs when some invaders mutate to overcome a drug and those bugs multiply. That resistance should fade when a drug’s use is stopped or reduced, or when multiple drugs are rotated over time, doctors said.
“Then we could presumably stay ahead of the bugs,” said Dr. John Bartlett, a Johns Hopkins infectious disease specialist.
For now, malaria drug combinations, including a new class of drugs should be used, along with insecticide spraying and treated bed netting, Dr. Nicholas White of Mahidol University in Bangkok wrote in an editorial. Financial help from richer countries will be needed, but could turn the tide on malaria, he wrote.
“Malawi is surrounded by a sea of chloroquine resistance,” White wrote, so it needs to be removed from use in Africa before it can come back.