Artemisinin-based combination therapy (ACT) resistance is widespread throughout the Greater Mekong Subregion. This raises concern over the antimalarial treatment in Thailand since it shares borders with Cambodia, Laos, and Myanmar where high ACT failure rates were reported. It is crucial to have information about the spread of ACT resistance for efficient planning and treatment. This study was to identify the molecular markers for antimalarial drug resistance: Pfkelch13 and Pfmdr1 mutations from 5 provinces of southern Thailand, from 2012 to 2017, of which 2 provinces on the Thai- Myanmar border (Chumphon and Ranong), one on Thai-Malaysia border (Yala) and 2 from non-border provinces (Phang Nga and Surat Thani). The results showed that C580Y mutation of Pfkelch13 was found mainly in the province on the Thai-Myanmar border. No mutations in the PfKelch13 gene were found in Surat Thani and Yala. The Pfmdr1 gene isolated from the Thai-Malaysia border was a different pattern from those found in other areas (100% N86Y) whereas wild type strain was present in Phang Nga. Our study indicated that the molecular markers of artemisinin resistance were spread in the provinces bordering along the Thai-Myanmar, and the pattern of Pfmdr1 mutations from the areas along the international border of Thailand differed from those of the non-border provinces. The information of the molecular markers from this study highlighted the recent spread of artemisinin resistant parasites from the endemic area, and the data will be useful for optimizing antimalarial treatment based on regional differences.
Artemisinin is the frontline fast-acting anti-malarial against P. falciparum. Emergence and spread of resistant parasite in eastern-India poses a threat to national malaria control programs. Therefore, the objective of our study is to evaluate the artesunate-sulfadoxine-pyrimethamine efficacy in Central India. 180 monoclonal P. falciparum-infected patients received standard ASSP therapy during August 2015-January 2017, soon after diagnosis and monitored over next 42-days. Artemisinin-resistance was assessed through in-vivo parasite clearance half-life (PC1/2), ex-vivo ring-stage survivability (RSA), and genome analysis of kelch13 and other candidate gene (pfcrt, pfmdr1, pfatpase 6, pfdhfr and pfdhps). Of 180 P. falciparum positive patients, 9.5% showed increased PC1/2 (> 5.5 h), among them eleven isolates (6.1%) showed reduced sensitivity to RSA. In 4.4% of cases, parasites were not cleared by 72 h and showed prolonged PC1/2(5.6 h) (P