Analysis of the dynamics of transmission of human schistosomiasis in the highveld region of Zimbabwe. A review.

With the starting point in a comprehensive and integrated longitudinal study conducted by the Blair Research Laboratory from March 1982 to May 1984 in Bushu and Chiweshe communal areas, a review is presented of the dynamics of transmission of urinary (Schistosoma haematobium) and intestinal (S. mansoni) human schistosomiasis in the highveld region of Zimbabwe. The study comprised observations on snail-related aspects of transmission, on human water contact patterns, and on prevalence, intensity and incidence of infection in the human definitive host population. S. haematobium was found to be of high endemicity whereas the endemicity of S. mansoni was moderate. This reflects that Bulinus globosus, the snail host for S. haematobium, is better adapted to the biologically unstable freshwater environments than Biomphalaria pfeifferi, the snail host for S. mansoni. The most essential findings comprise a marked seasonality and focality of transmission, an overdispersed distribution of infection, individual predisposition to infection, peak of prevalence and intensity of infection among children and young adults, a positive correlation between infection status in population subgroup and the relative transmission potential of water contact sites used, a pronounced specificity and marked conservatism in the human water contact pattern. The epidemiological background for schistosomiasis control strategies is outlined, and a community-based strategy within the primary health care system for schistosomiasis morbidity control is described. The community-based primary health care approach to schistosomiasis morbidity control is the strategy adopted in Zimbabwe.