Dicrocoelium dendriticum

Dicrocoelium dendriticum

Also known as:

Dicrocoelium lanceolatum Small lanceolate fluke

Dicrocoelium dendriticum - Joaquim Castellà Veterinary Parasitology Universitat Autònoma de Barcelona

Dicrocoelium dendriticum adult from horse faeces - Joaquim Castellà Veterinary Parasitology Universitat Autònoma de Barcelona

Scientific Classification

Kingdom	Animalia
Phylum	Platyhelminthes
Class	Trematoda
Order	Diagiorchiida
Family	Dicrocoeliidae
Genus	Dicrocoelium
Species	D. dendriticum

Hosts

Intermediate hosts: Land snails, mainly Zebrina detrita within Europe. Brown ants of the genus Formica are also required for completion of the life cycle.

Definitive hosts: D. dendriticum is most commonly seen in sheep, cattle, deer, and goats, but is occasionally seen in horses and pigs.

• This is a small fluke (<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 at grazing
  • 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 enhancing the likelihood of being eaten by grazing animals