COMPARATIVE HISTOPATHOLOGY OF BIOMPHALARIA-GLABRATA, BIOMPHLARIA-TENAGOPHILA AND BIOMPHALARIA-STRAMINEA WITH VARIABLE DEGREES OF RESISTANCETO SCHISTOSOMA-MANSONI MIRACIDIA

A comparative histopathological study of three snails species - Biomph alaria glabrata, B. tenagophila and B. straminea - which had been infe cted with Schistosoma mansoni miracidia revealed similar qualitative f eatures, consisting of areas of sporocyst proliferation and differenti ation associated with reactive host reaction, at the time they were ac tively eliminating great number of cercariae. However, in specimens th at Mere exposed to miracidia but failed to eliminate cercariae later o n, different histopathological pictures were observed in different sna il species. While B. glabrata exhibited frequent focal (granulomatous) proliferation of amebocytes in several organs, B. tenagophila and B. straminea only rarely showed such reactive changes, suggesting that th e mechanism of resistance to miracidial infection probably follows dif ferent pathways in the snail species studied.