Dicrocoelium dendriticum
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Dicrocoelium dendriticum
- This is a small fluke (less than 1.5cm) found in the bile ducts of ruminants and some other herbivores.
- The flukes migrate directly up the common bile duct to reach the bile ducts within the liver - they are therefore much less pathogenic than Fasciola (which burrow through the liver parenchyma).
- Dicrocoelium is rare in Britain, occurring mainly in the Hebrides, but is common in Europe.
- Small dark-brown eggs are shed in faeces.
- These contain a miracidium.
- If ingested by a land snail, the flukes develop, forming cercariae.
- These are excreted by the snails in slime-balls, which are collected and eaten by wood-ants.
- Metacercariae form inside the ants.
- The final host is infected when ants are eaten with grass.
- The presence of metacercariae in the nerve ganglia of the ants makes them revert to a primitive behaviour pattern, whereby they cling onto herbage overnight instead of retreating to the nest.
- This enhances the likelihood of being eaten by grazing animals.