FASCIOLA-GIGANTICA - THE PARASITE BURDEN IN LYMNAEA-NATALENSIS THAT DIED AFTER A CERCARIAL SHEDDING

Histological studies were carried out in lymnaea natalensis to determi ne why the number of Fasciola gigantica cercariae decreased when the p otent period duration increased. Observations were performed in snails killed between days 30 and 135 after exposure, and in snails that die d following a cercarial shedding between days 53 and 172 after exposur e (at 23 degrees C). Free and degenerated rediae became increasingly n umerous as experiment duration increased; hey represented 60% and more of the redial burden after day 135. Free and degenerated cercariae in creased in numbers after day 75, and predominated in older snails.