Submicroscopic Plasmodium falciparum infections before and after sulfadoxine-pyrimethamine and artesunate association treatment in Dienga, Southeastern Gabon.

BACKGROUND: It has been shown that Plasmodium falciparum submicroscopic infections (SMI) can contribute to malaria-associated anemia as well as to cerebral malaria. Polymerase chain reaction (PCR) assays are usually used as an alternative to microscopy in detecting subpatently infected individuals. OBJECTIVES: The main objective of this study was to investigate the occurrence of SMI before and after a suppressive antimalarial treatment in the population of the village of Dienga in Gabon. METHODS: Nested PCR was used to detect SMI and to determine genotypes. RESULTS: The prevalence rates of SMI were 13.67% (38/278) at day 0 and 8.99% (25/278) at day 14 after sulfadoxine-pyrimethamine-artesunate treatment. Genotype analysis of two polymorphic regions of the merozoite surface protein (MSP)-1 block 2, MSP-2 and a dimorphic region of the erythrocyte binding antigen (EBA-175) revealed that as many as 88% (22/25) of SMI detected after treatment were completely new alleles, indicating either previously sequestered parasites or newly acquired infections. CONCLUSION: These results demonstrate the usefulness of sulfadoxine-pyrimethamine-artesunate association treatment in the population of Dienga and confirmed early parasite genotype change after a suppressive antimalarial treatment in endemic areas.