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The genetics underpinning resistance to a frontline malaria drug, artemisinin, have been revealed, scientists say. In South East Asia, malaria parasites have developed tolerance to the treatment, and there are fears that this will spread. Now, in the largest genetic study to date, scientists have identified mutations in the parasite genome that are linked to resistance. The study is published in Nature Genetics. The researchers say the findings will help them to identify areas where artemisinin resistance could spread. Lead author Dr Olivo Miotto from the Mahidol-Oxford Tropical Research Unit (MORU), in Thailand, said: "Artemisinin is the best drug we have had for a very long time, and we want to continue this success story. "And for that its effectiveness has to be protected and sustained." When the first malaria drug, chloroquine, was developed, researchers thought that the disease would be eradicated within years. But the malaria parasite has proved far tougher than they ever imagined. Drug after drug has been rendered useless as the parasite has evolved to evade treatment. Mysteriously, each time resistance has emerged, it has started in the same place - on the Cambodia-Thai border - before spreading across Asia and into Africa. Now this appears to be happening again with artemisinin, a drug that has transformed malaria treatment. Cases have been confirmed in Thailand, Cambodia, Laos, Vietnam and Myanmar, also known as Burma. Now an international team of scientists have identified several mutations on genes in the malaria parasite that are linked to resistance. After analysing 1,612 samples from 15 locations in Asia and Africa, scientists confirmed that mutations on a gene called kelch13 are strongly associated with malaria resistance. "If you don't have this mutation of kelch13, you don't have resistance," Dr Miotto told the BBC.