Seasonality of Plasmodium vivax and P. falciparum in tribal villages in central India (1987-1995).

Microscopical examination of blood films produced from samples collected, over a 9-year period (1987-1995), from the inhabitants of four tribal villages of Mandla district, Madhya Pradesh (central India) revealed that malaria was highly endemic and probably transmitted perennially. Both Plasmodium vivax and P. falciparum were prevalent in all age-groups but their prevalence was highly seasonal: longitudinal studies showed an autumn (October-November) peak for P. falciparum and a summer (April-May) peak for P. vivax. However, both the incidence and prevalence of infection with each Plasmodium species showed inter-village variations. Analysis of the malariometric parameters investigated revealed that there had been no improvement in the malaria situation over the study period, and that, since 1992, there had been a shift in the predominant parasite, from P. vivax to P. falciparum, in each village.