Early Changes in Plasmodium falciparum Asexual and Sexual Populations in Children with Acute Infections Following Treatment with Artemisinin-Based Combination Drugs

Artemisinin-based combination therapies (ACTs) may influence malaria transmission but the early changes in parasite populations have not been frequently evaluated. The changes in Plasmodium falciparum asexual and sexual populations in the first 16 h following treatment with artemether-lumefantrine (AL) or artesunate-amodiaquine (AA) were evaluated in 443 children with acute infections. The effects of gametocyte density on gametocyte sex ratio (GSR) were characterized in another cohort of 52 children treated with AL and AA. Stages of asexual and sexual parasites in peripheral blood were determined morphologically. In 167 children there were significant increases in peripheral asexual parasitemia at 1 h, and in 15 of these, an insignificant increase in gametocytemia at 1 h, followed thereafter by a precipitous and significant fall in all patients. Time-course of GSR showed a female-male-female-biased cycle at 0 h, 4 h, and 8 h. Pre-treatment GSR and time-course of GSR post-treatment were independent of density in the additional cohort of 52 gametocyte carriers treated with AL or AA. Population changes were similar in ALand AAtreated children. Treatment with AL or AA is associated with early increases in asexual and sexual parasites and is closely followed by rapid elimination of these parasites.