The longevity of Fasciola hepatica metacercariae encysted on herbage

An experiment was described in which guinea pigs were used as tracer animals in an attempt to assess the longevity of Fasciola hepatic metacercariae on pasture at Werribee, Victoria. The metacercariae had been encysted on both an irrigated and non-irrigated area at various times during 1976. It was determined that, under the conditions of the experiment, metacercariae can survive and remain viable for up to 10 weeks during the winter. It was also determined that longevity during the summer was greatly reduced, and was of the order of only 1 week. The significance of these findings, with respect to the epidemiology of the disease, was discussed.