Artemisinin resistance has increased rapidly in the malaria-causing parasite, Plasmodium falciparum, along the border of Thailand and Myanmar, according to researchers from Thailand, the United Kingdom, and the United States (Phyo AP et al. Lancet. doi:10.1016/S0140-6736(12)60484-X [published online April 5, 2012]).
Rising failure rates with artemisinin-combination treatments (ACTs) have been noted in malaria clinics along the northwestern border of Thailand. In a study involving 3202 patients from these clinics who had been given oral ACTs over a 10-year period (2001-2010), the researchers found increases in the time taken to clear P falciparum parasites from the bloodstream, known as the parasite clearance half-life. The proportion of slow-clearing infections—with a half-life equal to or more than 6.2 hours—also increased during this decade, from 0.6% to 20%. Genetic analysis showed that this decline in clearance rates resulted from genetic factors that conferred artemisinin resistance.
Friedrich MJ. Artemisinin-Resistant Malaria. JAMA. 2012;307(19):2017. doi:10.1001/jama.2012.5079