Survival of snails and characteristic lesions of Fasciola hepatica infection in four European species of Lymnaea.

The survival of snails and characteristic organ lesions were investigated in four different age categories (new-born, 1 and 2 mm shell height, adults) and in four species of Lymnaea (L. glabra, L. palustris, L. peregra ovata, L. truncatula) infected by Fasciola hepatica. Mortalities were higher in infected groups on Days 30 and 45 post-infection (+42% and +45%, respectively) than in controls. Lesions depended on the species and age of the Lymnaea. Epithelial necrosis of the kidney was recorded in L. glabra, L. palustris and L. p. ovata, whereas intralamellar deposits were found in the same organ of L. truncatula. All categories of L. truncatula had evolutive infections (snails with living parthenitae); the young snails of other species became infected, but the adults did not, as estimated at Day 45 post-infection. The lesions were related to the intensity of evolutive infections: necrosis of the digestive gland was found in moderate to low infections and, conversely, gonadal atrophy with epithelial necrosis was found in highly infected snails.