Prevalence of antimalarial drug resistance markers and factors associated with Plasmodium falciparum infection in asymptomatic children prior to rectal artesunate implementation in Kapolowe Health District, Democratic Republic of the Congo

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BACKGROUND: In remote areas where access to parenteral treatment for severe malaria or referral is limited, rectal artesunate (RAS) followed by a full course of artemisinin-based combination therapy (ACT) provided by community health workers would be a pragmatic solution. However, concerns remain that its expanded use may select for artemisinin-resistant Plasmodium falciparum strains. This baseline study assessed the presence of molecular markers of resistance to artemisinin and partner drugs and investigated factors associated with Plasmodium falciparum infection prior to RAS implementation. METHODS: A community-based cross-sectional survey was conducted in remote areas of the Kapolowe health district, Democratic Republic of the Congo, in March-April 2024. Dried blood spot samples were collected from asymptomatic children aged 6-59 months. Molecular markers of antimalarial drug resistance in P. falciparum were analyzed using targeted next-generation sequencing, focusing on the Pfkelch13, Pfcoronin, Pfubp1, Pfmdr1, and Pfcrt genes. RESULTS: Among 1242 children screened in 906 households, 656 (53%, 95% CI: 50-55%) were P. falciparum malaria rapid diagnostic test-positive, of which 646 samples were available for analyses. Factors associated with reduced odds of asymptomatic P. falciparum infection included higher household socio-economic status and non-agricultural sources of income, whereas children from households where malaria was perceived as treatable had increased odds of infection. No validated Pfkelch13 mutations associated with artemisinin partial resistance were detected. Several non-synonymous Pfkelch13 mutations were observed more than once, including A578S (7/395, 1.8%). Two Pfubp1 mutations associated with reduced dihydroartemisinin susceptibility, D1525E (88/354, 24.9%) and E1528D (62/354, 17.5%) were observed. No resistance-associated Pfcoronin mutations were detected. The wild-type Pfcrt CVMNK haplotype predominated, while the Pfmdr1 NFSND haplotype (57/379, 15.0%) associated with reduced lumefantrine susceptibility was identified. CONCLUSIONS: The absence of Pfkelch13 mutations and a full reversal to wild-type Pfcrt are reassuring for directly guiding the implementation strategies of RAS and continued effectiveness of current ACTs. However, the detection of the Pfmdr1 single mutant NFSND haplotype highlights the need for continued monitoring of lumefantrine susceptibility.