Occurrence of a community with high morbidity associated with Schistosoma mansoni infection regardless of low infection intensity in north-east Brazil.

To establish the relationship between schistosome-associated morbidity and infection intensity in northeast Brazil, a parasitological and ultrasonographical study was carried out on 484 inhabitants of 4 villages (I, II, III and IV) in São Lourenço da Mata, Pernambuco, Brazil, where schistosomiasis is endemic. Quantitative stool examination using Knight's method demonstrated a high prevalence and moderate intensity of Schistosoma mansoni infection, and also that the subjects in village IV had a significantly lower prevalence and intensity of infection than those of the other villages. By ultrasonography, periportal fibrosis (PPF) and splenomegaly were found in 52% of the 299 infected subjects and 66% of the 146 infected subjects aged over 16 years old, respectively; 32% and 31% of the 299 infected subjects had abnormally high values of total bile acid (TBA) and alkaline phosphatase (ALP) activity, respectively. Liver and spleen size, PPF, and serum level of TBA and ALP were not correlated with infection intensity. There was no significant difference in the morbidity assessed by liver and spleen size, PPF, and serum analysis between the subjects in village IV and the other villages. These findings suggest the occurrence of a community with high morbidity associated with schistosomiasis regardless of low infection intensity.