Fasciola gigantica and F hepatica: a comparative study of some characteristics of Fasciola infection in Lymnaea truncatula infected by either of the two trematodes.

Experimental infections were carried out using three Lymnaea truncatula populations and two Fasciola species in order to determine the trematode influence on six parameters of snail infection by either of the two 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 of infected snails (from miracidial exposure to snail death), the increase in shell length throughout the experiment, the duration of the patent period and the number of cercariae shed by infected snails. The frequency of cercaria-shedding snails was closely correlated with the particular L truncatula population and trematode species. A similar finding 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 percentages of floating cysts were greater in the Fasciola gigantica groups than in the Fasciola hepatica groups.