Paris - Misuse of the world's most important anti-malaria drug is helping the disease's mosquito-borne parasite become resistant to the treatment, according to a study due to appear on Saturday.
Artemisinin, derived from a Chinese herb, has become the drug of choice for treating malaria after chloroquine, introduced in the 1950s, was rendered useless by resistance.
Researchers from the French-led Pasteur Institute Network took blood samples in 2001 from 530 malaria patients in Cambodia, French Guiana and Senegal, where there are different patterns of artemisinin use.
They then tested the samples in lab dishes, exposing the parasite, Plasmodium falciparum, to a range of malaria drugs.
Some samples from French Guiana and Senegal, where use of artemisinin is uncontrolled, showed signs of being insensitive to that drug. But samples from Cambodia, where the drug is controlled, showed no sign of resistance.
"All resistant isolates [samples] came from areas with uncontrolled use of artemisinin derivatives," said lead scientist Ronan Jambou. "This rise in resistance indicates the need for increased vigilance and a co-ordinated rapid deployment of drug combinations."
Extreme vigilance vital
The study appears on Saturday in The Lancet, the British medical weekly.
Its publication comes on the heels of a call on September 6 by the World Health Organisation (WHO), which called on countries to be extremely vigilant in the use of artemisinin-based drugs to avoid stoking resistance.
The new research pinpoints the problem to mutations in a gene in the parasite called SERCA-type Prtpase6 that is targeted by artemisinin.
Resistance by a bacteria, virus or parasite is encouraged when a patient fails to take a full course of drugs or uses drugs that are counterfeit or diluted.
Even though the symptoms may disappear, this action fails to kill all the microbes, leaving behind a colony that can reproduce and has a better chance of surviving an attack by those drugs.
Mutations can also occur randomly through sloppy replication of a microbe's genetic code or by swapping DNA with a counterpart which is slightly different. The change may affect those parts of the pathogen which are targeted by the drug.
Artemisinin is vulnerable to the counterfeiters as it is relatively expensive. It is nearly 20 times more expensive than chloroquine - at more than $2.40 per course, it is way beyond the means of many sufferers, especially in Africa.
The drug may also be facing resistance problems because the compounds with which it is sometimes administered as a combination therapy are ineffective.
Malaria kills around one million people every year and at least 300 million cases of acute malaria occur each year, according to the WHO, although some experts suggest this is a serious under-estimate.
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