Background Growing resistance of Plasmodium falciparum to Sulfadoxine-Pyrimethamine threatens the effectiveness of the intermittent preventive treatment during pregnancy with Sulfadoxine-Pyrimethamine (IPTp-SP) in malaria endemic areas. WHO recommends discontinuation in case of ineffectiveness as determined by over 95% and 10% prevalence of K540E and A581G mutants respectively. The objective of this study was to determine the prevalence of molecular markers of P.falciparum resistance to SP in the parasite population circulating in the south of Brazzaville and beyond, in the Republic of Congo.

Methods Two parallel surveys including hospital and community based cross sectional studies were carried out in the south of Brazzaville and beyond (urban, rural areas) between February 2021 and September 2022, to characterize the molecular markers of P.falciparum resistance to SP (dhfr and dhps). Restriction Fragment Length Polymorphism was used for the detection of single nucleotide mutation within the dhfr and dhps genes of the parasite, and detected mutations were further confirmed using Oxford nanopore sequencing platform.

Results High prevalence of mutations was reported for dhfr gene: N51I (100%), C59R (79.9%), S108N (100%), N164L (0.9%), and dhps gene: A437G (89.5%), K540E (42.4%), A581G (42.1%). The prevalence of the quintuple mutant (N51I+ C59R + S108N + A437G + K540E) and sextuple mutant (N51I+ C59R + S108N + A437G + K540E + A581G) were reported for 32.9% (111/337) and 20.8% (70/337) of the participants respectively while all the seven investigated mutations were reported in only one participant (0.3%). dhfr and dhps mutations were more prevalent in rural compared to the urban areas.

Conclusion These results indicate high prevalence of mutations within the dhfr and dhps genes of P. falciparum in south of Brazzaville and beyond in the Republic of Congo, which might threaten the effectiveness of IPT-SP in this area.