Effect of seasonality and ecological factors on the prevalence of the four malaria parasite species in northern mali.

Background. We performed 2 cross-sectional studies in Ménaka in the Northeastern Mali across 9 sites in different ecological settings: 4 sites have permanent ponds, 4 without ponds, and one (City of Ménaka) has a semipermanent pond. We enrolled 1328 subjects in May 2004 (hot dry season) and 1422 in February 2005 (cold dry season) after the rainy season. Objective. To examine the seasonality of malaria parasite prevalence in this dry northern part of Mali at the edge of the Sahara desert. Results. Slide prevalence was lower in hot dry than cold dry season (4.94 versus 6.85%, P = 0.025). Gametocyte rate increased to 0.91% in February. Four species were identified. Plasmodium falciparum was most prevalent (74.13 and 63.72%). P. malariae increased from 9.38% to 22.54% in February. In contrast, prevalence of P. vivax was higher (10.31%) without seasonal variation. Smear positivity was associated with splenomegaly (P = 0.007). Malaria remained stable in the villages with ponds (P = 0.221); in contrast, prevalence varied between the 2 seasons in the villages without ponds (P = 0.004). Conclusion. Malaria was mesoendemic; 4 species circulates with a seasonal fluctuation for Plasmodium falciparum.