Genetic Features of P. falciparum Parasites Collected in 2012-2016 and Anti-Malaria Resistance Along China-Myanmar Border

Abstract Backgrounds The therapeutic efficacy studies (TES) of T(DHA-PIP) for uncomplicated P. falciparum patients were implemented during 2012-2016 along China (Yunnan province)-Myanmar border, which verified the high efficacy of DHA-PIP. The study focusing on the genetic features of falciparum parasites and basing on in vivo parasite clearance time (PCT) were carried out to explore if they had produced potential resistance to DHA and PIP at molecular level. Methods The genetic features were investigated based on K13 propeller genotypes, Copy numbers of genes pfPM2 and pfmdr1 and 9 microsatellite loci (Short Tandem Repeats, STR) flanking the K13 gene on chromosome 13. The PCT 50s basing on different K13 genotypes, sites, periods and copy numbers were compared.Results In NW (North-West Yunnan province bordering with Myanmar) area, F446I prevalence was 58.96% (79/134). No significant different PCT 50s presented among 3 K13 groups (Chi-Square=2.35, P=0.31, df=2) classified by K13 genotypes within NW area, but all of them were significantly shorter than that in SW (South-West Yunnan province bordering with Myanmar) area (P=0.036, t=-2.11, df=174) where isolates only showed wild K13 genotype. For the copy numbers of pfmdr1 gene, 14.63% (18/123) and 62.5% (10/16) parasite isolates showed double copies (≥ 1.6) in NW and SW areas separately, but for those of pfM2 gene, no parasite isolates did. Between isolates with single and double copies of pfmdr1 gene, no different PCT 50 presented. According to the mean He values, the four K13 groups were arranged as ML group (Menglian County in SW), F446I group, Others (Non-F446I K13 mutation) group and W (wild K13 genotype) group from low to high. The mean Fst values between ML and W groups were significantly higher than other 2 K13 group-W pairs (Paired-T Test: t=-2.659，df=8，P=0.029; t=-4.966, df=8，P=0.001). Conclusions According to our study, P. falciparum isolates in NW area and SW area are very different in genetic features. Artemisinin partial resistance, inferred from genetic marker, F446I, had independently appeared and spread in NW area during 2012-2016. With global application of ACTs, this pattern of artemisinin resistance producing was worth more attention. Fortunately, PIP-resistant feature basing on genetic analysis showed negative results in both areas. So, DHA-PIP was still recommended in antimalarial treatment along China-Myanmar border based on molecular data, which was agreed with the conclusion drawn from in vivo data obtained with same falciparum isolates. Trial registration: ISRCTN, ISRCTN 11775446. Registered 13 April 2020 - Retrospectively registered, http://www.isrctn.com/ISRCTN11775446.