finally establishes itself in the bile duct after entering and feeding on the
liver. Having matured, it eventually produces quite large eggs
(150 90 mm) which have a lid, or operculum, at one end. These are
secreted in the faeces after passing from the bile duct to the alimentary
tract.
The eggs hatch in water to produce a highly ciliate and motile embryo
(miracidium) which cannot infect the definitive host and has to infect a
species of water snail such as Limnaea truncatula. There are several
stages in this secondary host, some leading to multiplication of the
parasite, but eventually the organism is released as the final larval stage
(cercaria) which encyst and may survive for up to a year depending on
Figure 8.1 Life cycle of the liver fluke,Fasciola hepatica
Chapter 8 271