Scientists have discovered genetic markers in malaria parasites linked to resistance to the key anti-malarial medicine piperaquine, and say their work could help doctors and health officials monitor and limit the spread of such resistance.

In research published in the Lancet Infectious Diseases journal, the team also said a simple test using blood taken from a finger pinprick could show whether a malaria patient has parasites with the genetic markers - allowing doctors to prescribe an alternative treatment.

Resistance to piperaquine recently emerged in Cambodia and has led to the complete failure of malaria treatment there. This and other spreading areas of drug-resistance are threatening global efforts to eliminate the mosquito-borne disease.

Piperaquine is a powerful drug which is used in many parts of the world in combination with another anti-malarial drug called artemisinin.

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Resistance to artemisinin emerged around seven years ago in Southeast Asia, but until recently the combination of the two drugs had successfully killed the malaria parasites there. Now, however, the emergence of piperaquine resistance in Cambodia has led to treatment failing altogether.

"These malaria parasites are now resistant to both drugs, and since they are no longer being killed, resistance to both drugs will spread," said Roberto Amato, who co-led the research at Britain's Sanger Institute.

According to the World Health Organization, an estimated 200 million people worldwide were infected with malaria in 2015, and nearly half a million people died from the disease. The vast majority of those killed by it are children under five.

Malaria is treatable if it is caught early, but growing drug resistance is becoming a major problem in many areas.

For this study, Amato's team worked with Rick Fairhurst, a professor at the National Institute of Allergy and Infectious Diseases at the United States National Institute of Health, and carried out what is known as a genome-wide association study to look at the genetic basis behind piperaquine resistance.

They looked at around 300 samples from Cambodia, analyzing thousands of variations in the DNA sequence of the parasites and comparing these across samples with different levels of resistance to piperaquine.

"By studying the genomes of these parasites we found two genetic markers that are linked with piperaquine resistance," Amato said. "Not only can we now use these markers to monitor the spread of the drug resistant malaria, they will also help towards understanding as much as possible about the biology and evolution of the (malaria) parasite."