Dicrocoelium dendriticum

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.