Infecção natural e formas evolutivas de Echinostoma revolutum (Fröelich, 1802) em Biomphalaria tenagophila (Orbigny, 1835) e Rattus norvegicus. Susceptibilidade de Mus musculus ao parasitismo

Abstract

In order to study natural infection of Echinostoma revolutum in Rattus norvegicus and in Biomphalaria tenagophila from the district of Posse, Nova Iguaçu, RJ, Brasil, as well as the infection of this trematode on the Mus musculus mouse under laboratory conditions, several B. tenagophila snails were collected, being show that some of these specimens released Echinostomocercariae. Shell fragments and rat feces were found in the habitat of these mollusks and stool examination revealed trematode eggs (about 20 eggs per microscopical field). Thirty-eight (38) trematodes were taken from the small intestine of a captured specimen of R. norvegicus. These worms were identified as E. revolutum. The following evolutive stages were observed: egg, miracidium, rhedia II and cercaria. Although the metacercaria stage was not found, its occurrence in B. tenagophila and Physa sp. became evident since M. musculus mice infected with cercariae from this mollusks released eggs of E. revolutum in their stools (18) eighteen days after infection. These snails were considered as first and second intermediate host, respectively, for the spread of E. revolutum in nature, while B. tenagophila may act simultaneously as the first and second intermediate host. It was also seen that R. norvegicus and M. musculus are excellent definitive hosts for E. revolutum in nature and in the laboratory, respectively. xvi. The relationship between E. revolutum and R. norvegicus may be regarded as an Anthropozoonosis, an important condition to be considered in campaigns against schistosomiasis which use E. revolutum as biologic control measure.