A clinico-epidemiological survey of schistosomiasis mansoni in a hyperendemic area in Minas Gerais State (Comercinho, Brazil). I. Differences in the manifestations of schistosomiasis in the town centre and in the environs

A cross-sectional survey of schistosomiasis was done in Comercinho (Minas Gerais State, Brazil). Faecal (Kato-Katz technique) and physical examinations were performed on 90% and 79% of the population (1474 inhabitants), respectively. The rate of infection with Schistosoma mansoni was 70%, the geometric mean of eggs was 334/g of faeces and 7% of the infected individuals had splenomegaly. The rate of infection, faecal egg counts and the rate of splenomegaly were significantly higher in the environs (zones 3 and 4) of the town than in the central areas (zones 1 and 2) of Comercinho. This difference seemed to be determined by the social differences existing between the population in the central area and the environs; in the environs the heads of families were predominantly manual workers (73 and 94% respectively), only 10 and 3% of the houses had piped water supply and less than 14% were of better quality.