Resistance Fears As 'life-saver' Malaria Drug Loses Potency

A new class of malaria drugs that has been billed as a life-saver for millions of children in Africa and Asia is already losing its potency, scientists warn today in a paper that also suggests the drugs may be being used without proper regulation or controls in some countries.

Experts described the study, showing resistance developing to artemisinin drugs, now universally recommended for malaria treatment by the World Health Organisation, as "a wake-up call".

The content of the paper, which has been published in the Lancet medical journal, will dismay those who have been striving to cut the death toll from malaria of more than a million people a year, 70% of those being children under the age of five and babies.

Resistance to malaria drugs has always been a problem but had become so serious that some of the older drugs, such as choloroquine and, in east Africa, the combination of sulfadoxine-pyrimethamin, had become virtually useless.

Artemisinin compounds, made from plants growing in China, have been widely seen as the answer. They are supposed to be used in combination with other drugs, so as to reduce the chances of the malaria parasite, Plasmodium falciparum, developing resistance to them. A combination of artesunate (an artemisinin derivative) and the older drug mefloquine has been used successfully in Thailand for 10 years without resistance developing.

But scientists from the Pasteur Institute Network report in the Lancet that they found resistance to artemisinin in blood samples from patients in Senegal and in French Guiana. In both countries, they said, the drugs were not being used with proper controls.

The scientists, Ronan Jambou, Eric Legrand and colleagues, also tested blood from patients in Cambodia, where the drugs are controlled, and did not find resistance in those samples.

In French Guiana the scientists uncovered resistance in Cacao, a small town where artemisinin derivatives were being illegally imported from south-east Asia. Resistance was also found in the gold mining region along the Maroni river, where people were treating themselves with illegally imported artemisinin drugs.

In Senegal the artemisinin drugs were being given alone, and not in combination with other anti-malarials, as is normally recommended.

The laboratory tests did not prove that the artemisinin drugs were no longer working in these geographical areas, the researchers said, but it was "the probable first step of an alarming cascade and definitely pleads for increased vigilance and a coordinated and rapid deployment of drug combinations".

In a commentary, Patrick E Duffy and Carol Hopkins Sibley, from the Seattle Biomedical Research Institute, warn that "the expectation that all combinations with artemisinins will have a long therapeutic life may be overly optimistic".