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The liver fluke F. hepatica has a complex life cycle. There are typically 6-8 stages the liver fluke typically goes though. These can be followed along in the diagram to the left.
The liver fluke F. hepatica has a complex life cycle. There are typically 6-8 stages the liver fluke typically goes though. These can be followed along in the diagram to the left.
Immature ova is passed in the feces of infected animals. When this fecal material is in cool wet grass the ova is allowed to mature into the next step.
An embryo develops inside the ova due to the ideal conditions being met
The first immature stage of the liver flukes, the miracidia, hatches from the ova. It resides in the moisture of the pasture and will constantly seek out the intermediate host, a snail. The miracidia only has 3 hours to do this before it dies off.
Once the miracidia infects the snail it goes through a series of changes in the snails small intestine. It goes from a miracidia to a sporocyst, a rediae and finally a cercariae. From only one miracidia, hundreds of cercariae can form.
5. After approximately 6 weeks, the cercariae will emerge from the snail, though this can depend on climate. Using their tails they will swim to attach themselves to near by herbage.
6. The cercariae lose their tails when they attach and develop a hard outer membrane and become metacercarie. These are what can be digested by ruminates and humans to cause infection.
7. Once inside the body the metacercariae transitions to an immature fluke which burrows through the wall of the small intestines to reach the bile duct and the liver.
8. These immature flukes grow and develop while feeding off the liver and will pass ova of their own. That completes the cycle.
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