RESULT
Non-infected snails (Fig.1) showed normal histology of the digestive tract with appearance of normal columnar epithelia (Ec) and secretary (Sc) cells. Cells are settled on the basal portion of the cell. Fig. 2 shows obvious histological changes in the digestive gland of snails infected with S. mansoni with large numbers of sporocysts and cercariae at different developmental stages encircled by cycts. Infection of snails with S. mansoni miracidia caused great damage in the epithelial region of B. alexandrina, the cells seemed to be empty, secretary cells disappeared and connective tissue was damaged.
The different shapes of haemocytes observed through the scanning electron microscopy did not wholly confirm those reported under the light microscopy, so special emphasis was given to the surface structure.