The findings in the U.K.-based publication released on Friday observed that patients at malaria clinics took longer to get better when treated with combination therapies containing artemisinin - a drug derived from the sweet wormwood shrub and which is recognized as the best drug against malaria, according to one of the authors.

"The malaria strains that are resistant to artemisinin are definitely found in the western border of Thailand and eastern Myanmar," said Professor Nicholas White at the Mahidol Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, in Bangkok, Thailand, and Centre for Tropical Medicine, University of Oxford.

"The implications are that they either spread or emerged newly there," White told Reuters by telephone.

The spread of drug-resistant malaria has been blamed on the incorrect use of artemisinin and fake and substandard versions of the drug. Stronger action was needed from governments and international health agencies to stop all that, White said.

"We need considerable support for Myanmar, leadership, better intelligence on where (drug-resistant malaria) is spreading ... it's like fighting a war," White said.

"We need serious financial support to contain it in this region, otherwise it is going to spread to India and Africa where more people can be affected."

White and his colleagues do not know if this malaria strain that is now spreading in Myanmar is linked to the one that emerged in Cambodia eight years ago, and they will analyze their genes next to see if they are related.

"We will be able to get a clearer answer to that within the next year by looking at the full genome ... (to tell) whether they have the same origin or not," White said.

White and his team studied 3,202 patients between 2001 and 2010 who were infected by the Plasmodium falciparum, a species of malaria that can cause severe disease. They found that the standard treatment containing artemisinin took significantly longer to clear the parasites from their bodies.

"None of the patients died, but the drugs (were) not working as well as they did before," White said.

"If you have life-threatening malaria, the best treatment is artesunate (derivative of artemisinin) - the treatment of choice throughout the world. Compared with quinine, it reduces death by a-third. We could lose that advantage," White said.

Malaria is caused by the parasite Plasmodium transmitted through the bites of infected mosquitoes. Symptoms include fever, headache and vomiting. If not treated, it can kill by disrupting blood supply to vital organs.

It killed an estimated 655,000 people in 2010, or 1,794 each day, mostly African children.

(Reporting by Tan Ee Lyn; Editing by Ed Lane)

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