Repeated mass treatment of schistosomiasis mansoni: experience in hyperendemic areas of Brazil. I. Parasitological effects and morbidity

Abstract
The current project, carried out in Viçosa (state of Alagoas, Brazil), sought to assess the impact of repeated mass treatment campaigns (4 times over a period of 5 years) upon the prevalence, egg counts and morbidity of schistosomiasis mansoni. Results were not impressive. Some control seems to have been achieved in zones of the town better-off in terms of sanitation and socio-economic conditions, while in other areas no effect whatsoever of chemotherapy was detected. Neither resistance to the drug (oxamniquine) nor its deterioration could be held responsible, since a short-term follow-up of a group of children personally treated by the authors showed rapid reinfection, after an excellent initial response. This study, complemented by data from an area in Pernambuco and a hospital survey over the period 1978–1984, indicated that morbidity due to schistosomiasis was decreasing, although there was some evidence that other factors may be at least partly responsible for the increasing scarcity of “hepatosplenic” schistosomiasis. Schistosomiasis, a strictly focal problem, thus calls for a targeted approach to control. It is believed that chemotherapy alone will not suffice and that sanitation, vector control and, perhaps, health education are equally essential in areas which remain refractory to mass treatment.