Fasciola hepatica is the only species of this genus to infect sheep in Australia. Paramphistomes comprise several species. The life cycle is indirect and involves a snail intermediate host. Species include Lymnaea tomentosa and L. columella . In order to assist identification, note that with the apex of the shell pointing away the opening is to the right.
Open water is essential for survival of free living stages and for the snail habitat.
In addition to needing a sheep as a host, the fluke needs open water, warmth as well as a snail intermediate host for its development. Eggs are deposited in the faeces of infected sheep but only eggs that end up in snail-infested areas can stay in the cycle. The miracidia and the cercaria, the stages which enter and leave the snail, respectively, also need water. Metacercaria, which are the infective stage for sheep, survive up to a year in cool moist conditions. The lymnaeid snails prefer slow moving water and are usually found in boggy areas and dams.