Proposition of a simple method for the production of Fasciola hepatica metacercariae from the snail Lymnaea truncatula

Fasciola hepatica infections of Lymnaea truncatula (2 miracidia/snail) were performed to study metacercaria production in relation to the snail confinement in petri dishes (1 or 2 snails/dish). Snails originated from two populations living at 500 and 750 m in altitude, and were fed on lettuce steeped by a 5-day immersion in spring water. The prevalence of infection was 82 % in the snails from Courcelles 1 (1 snail/dish), 63 % in those from Courcelles2 (2 snails/dish), and only 45 % in those form Saint-Ours (1/dish). The total number of metacercariae per cercaria-shedding snail was 107.0, 56.2, and 56.5, respectively. The mean number of metacercariae recorded in the Courcelles2 group until the day 8 of the shedding period was significantly higher than those noted in the two other groups. The method for L. truncatula breeding using steeped lettuce give a good production of parasites (more than 42,000 metacercariae originating from 581 cercaria-shedding snails over 3 weeks). In contrast, the confinement of 2 snails in each petri dish was unfavorable on metacercaria production and must be avoided, even though cercaria exit from snails was stimulated during the first 8 days of the shedding period.