[Epidemiology of human bilharziasis].

Schistosomiasis is endemic in three continents: Africa, where Schistosoma haematobium, S. mansoni and S. intercalatum are present; tropical America and some of the the Caribbean islands, where the only parasite of this type is S. mansoni; Mediterranean Asia (S. haematobium, S. mansoni) and the Far-East (S. japonicum, S. mekongi). Schistosomal infestation is distributed in foci of warying size and significantly differs in prevalence, intensity and therefore morbidity from one region to another. Despite the successes obtained in the neutralization of certain foci, the great plasticity of the hosts-parasites-molluscs relations and the huge displacements of human populations in the poorer countries explain why the epidemiology of schistosomiasis is constantly changing and the disease is far from disappearing.