Sequential histological changes in Biomphalaria glabrata during the courseof Schistosoma mansoni infection

Biomphalaria glabrata, highly susceptible to Schistosoma mansoni, were seen to shed less and less cercariae along the rime of infection. Histological examination kept a close correlation with this changing pattern of cercaria l shedding, arming an initial picture of no-reaction (tolerance) gradually into one of hemocyte proliferation with formation of focal encapsulating le sions around disintegrating sporocysts and cercariae, a change that became disseminated toward the 142nd day post miracidial exposure. Findings were s uggestive of a gradual installation of acquired immunity in snails inferred with S. mansoni.