Fasciola hepatica

Fasciola hepatica (liver fluke)

The life cycle of liver fluke

Adult liver fluke lay eggs in the bile ducts of a host animal (usually sheep or cattle) that are then passed out onto pasture in the host’s faeces. Even in a light infection a liver fluke can produce up to 25,000 eggs a day. One infected sheep can deposit up to 500,000 eggs a day.

While on the pasture liver fluke eggs develop into embryos and hatch, releasing miracidia. These miracidia then seek out and infect snails, using them as an intermediate host.

The miracidia develop further in the host snail and multiply into infective cercariae. The snail sheds these cercariae, which then migrate to wet herbage where they encyst as metacercariae. At this stage the final host animal eats them.

The metacercariae excyst in the duodenum of the host and migrate through the intestinal wall, the peritoneal cavity and the liver parenchyma into the bile ducts. From here they develop into adult fluke and the cycle begins again.

Liver fluke infection is obvious in the host about 10 – 12 weeks after they have eaten the metacercariae. The whole cycle takes 18 – 20 weeks.

You can find more information on the impact of liver fluke here.

Liver fluke physiology

An adult liver fluke is among the largest of flatworms and can reach a length of approximately 30mm. They have a conical projection, oral and ventral sucker pharynx, branched caecum and a coiled uterus.

A viable metacercaria is approximately 0.2mm in diameter and contains flame cells within the cyst wall. If a metacercaria viewed under a dissecting microscope does not have flame cells then it is deemed to be nonviable.

Liver fluke we supply

We culture parasites on request.

We offer eggs, metacercariae and adult life cycle stages of liver fluke.

We can also supply triclabendazole susceptible and resistant strains.