Frequencies of molecular markers of drug resistance in the context of two different Seasonal Malaria Chemoprevention (SMC) treatment regimens in the Koulikoro health district, Mali.

With growing concern about parasite resistance to sulfadoxine-pyrimethamine (SP) in West Africa, the effectiveness of dihydroartemisinin-piperaquine (DHA + PQ) was assessed as an alternative drug regimen for Seasonal Malaria Chemoprevention (SMC). This study aims to determine the prevalence of molecular markers of resistance to SP + AQ and DHA + PQ in Koulikoro (Mali), where SMC has been implemented since 2014. Plasmodium falciparum-positive samples were analyzed by either next-generation sequencing, focusing on SNPs in genes known to be associated with resistance: Pfmdr1, PfK13, Pfcrt, Pfdhfr, Pfdhps, and Pfexo genes, and using qPCR for copy number variations (CNVs) of Pfmdr1 and Pfplasmepsin2. A total of 564 PCR-positive P. falciparum samples were analyzed: 218 in 2019 and 346 in 2020. In both years, the Pfdhfr 51I-59R-108N haplotype was highly prevalent (>93%). In both arms, the Pfdhps single mutant (437G) was the most prevalent (~60%). In 2020, the combined haplotype Pfdhfr/Pfdhps IRN/IAGKAS and IRN/VAGKGS was detected at 9.6% and 1.2%, respectively. The Pfmdr1 haplotype (N86-F184-S1034-N1042-D1246) represented more than 52.0%, and no difference was observed between the years, while a significant increase in the Pfcrt wild-type haplotype (C72-V73-M74-N75-K76) from 39% in 2019 to 52% in 2020 (P = 0.01) was observed. Some PfK13 non-synonymous mutations were observed in both years, including Y493H and C580R. The identification of the IRNI/IAGKAS quintuple mutant, along with emerging Pfdhps-431V and non-synonymous PfK13-Y493H variants, underscores the importance of continued surveillance of resistance markers.