The characteristics of redial generations in Lymnaea truncatula exposed to Fasciola hepatica miracidia after poisoning by sublethal doses of cupric chloride.

Adult Lymnaea truncatula were placed in a sublethal dose of copper chloride (0.1 mg/l) for 1 h, and then in normal water before being exposed to a single Fasciola hepatica miracidium on the 2nd or 9th day of the experiment. Infection rates were higher in untreated snails and in snails infected 9 d after treatment (73.5 and 71.4%) then in snails infected 2 d after copper contact (48.1%). Histological examination of surviving snail on the 30th day after miracidial exposure revealed that the total number of rediae was 25 and 31 per snail in snail groups infected 2 and 9 d respectively after copper contact, and 44 in untreated controls. There was a drop in the number of live, free rediae in infected snails after treatment contact. This decrease was more marked in the first redial generation than in the first cohort of the second generation. These results reveal that the infection rate in snails and the redial burden of F hepatica were reduced by the copper treatment of snails before miracidial exposure but placement of survivors in water for 8 d after treatment limited the consequences of chemical toxicity.