Trajectory of Plasmodium falciparum Molecular Markers of Amodiaquine Resistance in São Tomé and Príncipe

Artesunate-amodiaquine has been the first-line treatment for uncomplicated malaria in São Tomé and Príncipe since 2005, following many decades of chloroquine usage. We evaluated the recent dynamics in prevalence of the Plasmodium falciparum amodiaquine-resistance-associated pfmdr1 86Y/Y184/1246Y haplotype, by analyzing infections from the 2020-2022 period and comparing them with historical data. The results suggest that the introduction of artesunate-amodiaquine led to a trajectory of single nucleotide polymorphism (SNP) successive accretion in a pre-existing environment of pfcrt 76T near fixation, leading to the emergence of a dominant 86Y/Y184/1246Y haplotype. Our data support increased vigilance of artesunate-amodiaquine performance in São Tomé and Príncipe.