Wellcome researchers have found that genetic mutations in the kelch gene of the malaria parasite have made the parasite resistant to the anti-malaria drug mefloquine and the drug artesunate.
These drugs are typically used in combination to treat malaria. This treatment, known as artemisinin combination therapy (ACT), is now failing.
Researchers analysed data from a ten-year study of 1,005 patients with uncomplicated Plasmodium falciparum malaria at Shoklo Malaria Research Unit (SMRU) clinics on the Thai-Myanmar border.
"This study demonstrates for the first time that artemisinin resistance leads to failure of the artemisinin partner drug, in this case, mefloquine. This means that the first-line artemisinin combination therapy introduced here in 1994 has finally fallen to resistance," said Professor François Nosten, Director of SMRU.
Resistance to ACTs poses a serious threat to the global control and eradication of malaria. If drug resistance spreads from Asia to the African sub-continent, or emerges in Africa independently, millions of lives will be at risk. Most of them will be children in Africa aged under five.
SMRU, which is a unit of the Bangkok-based MORU, is based in the refugee camps and migrant communities along the Thai-Myanmar border in northwest Thailand.