FASCIOLA-GIGANTICA AND FASCIOLA-HEPATICA - A COMPARATIVE-STUDY OF SOME CHARACTERISTICS OF FASCIOLA INFECTION IN LYMNAEA-TRUNCATULA INFECTEDBY EITHER OF THE 2 TREMATODES

Experimental infections were carried out using three Lymnaea truncatul a populations and two Fasciola species in order to determine the trema tode influence on six parameters of snail infection by either of the t wo trematodes. All experiments were performed using snails 4 mm long, two miracidia for each L truncatula, and a constant temperature of 20 degrees C. No significant influence of trematode species was detected in the following parameters: snail survival at day 30, the life span o f infected snails (from miracidial exposure to snail death), the incre ase in shell length throughout the experiment, the duration of the pat ent period and the number of cercariae shed by infected snails. The fr equency of cercaria-shedding snails was closely correlated with the pa rticular L truncatula population and trematode species. A similar find ing in two populations was also noted for the frequencies found in the infected snails who died without emission. The prepatent period had a longer duration in the Fasciola gigantica-infected groups. The percen tages of floating cysts were greater in the Fasciola gigantica groups than in the Fasciola hepatica groups.