Determinants of Malaria Parasite Clearance Time Following Artemisinin-Based Combination Therapy in Children Under Five in Oyo State

Delayed parasite clearance following artemisinin-based combination therapy is a recognised early indicator of artemisinin partial resistance, and identifying host and parasite determinants of clearance kinetics in Nigerian children is clinically urgent. This analytical study examined determinants of parasite clearance time among 280 children aged 6 months to 5 years with uncomplicated falciparum malaria treated with artemether-lumefantrine at a secondary health facility in Oyo State, Southwest Nigeria. Blood samples for thick film microscopy were collected at 0, 8, 24, 48, and 72 hours post-treatment initiation. Parasite clearance half-life was calculated using the Worldwide Antimalarial Resistance Network protocol. Dried blood spot samples were analysed for K13 mutations and initial parasite density. Host factors including age, nutritional status, and haemoglobin level were recorded. Mean parasite clearance half-life was 3.2 hours, with 6.4 percent of children demonstrating slow clearance (half-life greater than 5 hours). High initial parasitaemia and low haemoglobin were the strongest predictors of slow clearance. K13 mutations were identified in three of eighteen slow-clearing cases. These findings provide empirical data for the national therapeutic efficacy surveillance network and highlight the need for prospective clearance monitoring in sentinel sites. Keywords: parasite clearance, artemether-lumefantrine, artemisinin partial resistance, children, Oyo State.