Seasonal patterns of Plasmodium falciparum gametocyte prevalence and density in a rural population of Burkina Faso.

Gametocytes are the malaria parasite stages that secure the transmission from the human host to the mosquito. The identification of natural parameters that influence gametocyte carriage can contribute to a better understanding of the dynamics of the sexual stage parasites for transmission reducing strategies. A total of 3400 blood slide readings were done during four cross-sectional surveys (2002-2003) including all age groups to determine the effect of season on Plasmodium falciparum gametocytes in a seasonal malaria transmission area of Burkina Faso. Entomological data were collected to determine the malaria transmission intensity in relation to seasons. Transmission intensity was estimated by monthly EIRs, averaging 28 and 32 infective bites/person/month in the wet seasons of 2002 and 2003, respectively. The EIR in the dry seasons was below one infective bite/person/month. The gametocyte prevalence was significantly higher at the start and peak of the wet season compared to the dry season when corrected for asexual parasite density and age. Gametocyte density significantly increased during the wet season after correction for asexual parasite density and age. In this study, season appears to be an independent parameter that determines gametocyte prevalence and density and should be considered to be included in epidemiological studies on malaria transmission.