Dynamics of ACT parasite clearance in falciparum malaria among a cohort of inhabitants in a malaria hyper-endemic focus, Ilorin Nigeria

Background An appreciable reduction in parasite clearance time (PCT) following artemisinin combination therapy (ACT) is a strong prognosis for resistance, which hitherto threatens the global malaria elimination. The study exposits the accurate measurement of PCT following clinical ACT regimen among inhabitants in a malaria hyper-endemic focus, Ilorin, Nigeria. Methods Malaria-positive in-patients were periodically administered ACT and their parasitaemia was determined microscopically at 0, 12, 24, 36 and 72 hours. The data obtained were uploaded on the world wide antimalarial resistant network (WWARN). Results One hundred and twenty-one (121) valid malaria cases were evaluated using established algorithm. The following ensued, viz; lag-phase (10); median positive parasite slide (0.09) per patient; range (0.04–0.10); interquartile range (0.08–0.09); clearance rate/hour constant (K, 1/hour); distribution (N = 3, 2.48%, 0-0.05) and (N = 118, 97.52%, 0.05–0.10) respectively. The slope half-life median (range; IQR) of 7.96 (7.22–15.47; 7.74–8.42) hour. Parasite clearance was as follows; 50% (13.30; 11.86–16.78; 13.21–13.34), 90% (32.00; 30.75–47.79; 31.53–33.08), 95% (40.06; 38.23–63.26; 39.38–41.19) and 99% (58.20; 55.59–99.19; 57.55–60.74) per hour of initial value. The minus slope of the Tobit regression revealed three models, viz; best fit at 50hours (Type I); 30hours (Type II) and 20hours (Type III). Conclusion The dynamics with delayed parasite clearance does not entirely reflect ACT failure, but it is pertinent to monitor other early signs of resistance. Artemisinin derivatives still remain the drug of choice because of its half-life and the potentials for eliminating early ring stage.