Molecular surveillance of drug resistance markers in Plasmodium falciparum isolates from Ghana

The emergence and spread of Plasmodium falciparum drug-resistant parasites remain a significant hurdle to malaria control and elimination. However, how changes in transmission affect the evolution of drug resistance remains incompletely understood. We investigated the spatiotemporal prevalence of drug resistance across three distinct eco-epidemiological zones of Ghana (Guinea Savannah, Forest and Coastal) by characterizing genetic polymorphisms in five drug resistance genes ( pfdhfr, pfdhps, pfmdr1, pfk13 and pfmdr2 ). A total of 764 P. falciparum isolates collected between 2010 and 2017 were analyzed using amplicon sequencing. The artemether lumefantrine (AL) resistance-associated genotypes, pfmdr1 -N86 and pfmdr1 -N 86 F 184 D 1246 , were near fixation in the Forest zone (90-100% and 63.9-100%, respectively). The prevalence of pfmdr1 -N86 also increased significantly over time in the Guinea Savannah and Coastal zones (χ2 = 7.13, P<0.05; χ2 = 7.19, P<0.05). Regarding artemisinin (ART) resistance, none of the validated Southeast Asian pfk13 mutations were detected. We also characterized mutations in pfmdr2 , another ART resistance-associated gene, for the first time in the Savannah and Forest zones of Ghana. For sulphadoxine-pyrimethamine (SP) resistance, the resistance-conferring alleles pfdhps - 540E and pfdhps - 581G occurred at prevalences below 5% and 10%, respectively. Similarly, the pfdhfr/pfdhps -I 51 R 59 N 108 G 437 E 540 haplotype, associated with full SP resistance, was detected in fewer than 5% of parasites. The observed resurgence of parasites carrying the chloroquine (CQ)-sensitive proxy marker pfmdr1 -N86, together with the increase in CQ-wildtype marker ( pfcrt -K76) prevalence reported in other studies, suggests that CQ sensitivity is re-emerging and may inform future consideration of CQ-based combination therapies. Additionally, the rarity of the pfdhfr/pfdhps -I 51 R 59 N 108 G 437 E 540 and pfdhfr/pfdhps -I 51 R 59 N 108 G 437 E 540 G 581 haplotypes, driven by the low prevalence of pfdhps - 540E and pfdhps - 581G alleles, supports the continued use of SP for preventive therapy in Ghana.