Four British citizens who caught malaria while travelling in Africa have shown apparent resistance to the main drug used to treat the disease, according to researchers at the London School of Hygiene and Tropical Medicine.
Scientists say the discovery should act as a warning for Africa, where the drug has played a key role in sharply reducing mortality rates from malaria.
The four travellers were treated with a drug called Artemether-Lumefantrine after returning to Britain from different parts of Africa within a five-month period, showing symptoms of malaria.
The cases alerted scientists at the London School of Hygiene and Tropical Medicine, led by Dr. Colin Sutherland.
“This drug is normally expected to cure someone after a three-day course and they are sent home once their blood films show that there is [are] virtually no parasites left. And in each case, these patients seemed to have a clear blood film, or very close to a clear blood film, and were sent home with an apparent clean bill of health, only to return three to seven weeks later,” said Dr. Sutherland.
The drug is part of a treatment known as Artemisinin Combination Therapy or A-C-T, widely used across Africa, where most malaria cases and deaths occur. These are among the first cases of apparent reduced susceptibility to the treatment.
“If it is under threat from resistance, and we have not absolutely ascertained that is the case but we suspect it is, [it's] certainly time now to look very carefully at that. If it is under threat, then that is a serious issue and we need to take steps,” said Dr. Sutherland.
Such steps might involve using other drugs alongside A-C-T. But such a change of strategy takes time, said Sutherland.
“Of course a lot of malaria is in the countryside, it is in district hospitals and bush clinics. You can not just say, ‘Let us try a different drug,’ if it is not available at the time. So that requires planning and forethought,” he said.
Resistance to A-C-T drugs is an ongoing problem in parts of Southeast Asia. But the resistance shown by the malaria parasites in these four cases is unrelated, Sutherland said.
“Whatever it is that is happening in Africa, these four patients do not represent the kind of resistance that has become really a quite serious problem in Southeast Asia,” said Dr. Sutherland.
Chinese scientist Professor Youyou Tu won the 2015 Nobel Prize in Medicine for her discovery of Artemisinin as a treatment for malaria. Its widespread use has contributed to a 30 percent fall in malaria deaths worldwide between 2010 and 2015.
Scientists say the latest cases of apparent resistance are a warning, and should be investigated further.