Liver Cestodes

• tapeworms
• have both intermediate and final hosts in their life cycle
• main expression in the UK are the encysted forms that utilise the liver and other organs in intermediate hosts

Taenia hydatigena

• the most important species
• final host
  • dog
  • alimentary tract
• intermediate host
  • ruminant, horse, or pig
• life cycle is completed when the carnivore eats the tissues of the intermediate host containing the cysts
• the intermediate stage - Cysticercus tennuicollis
  • fluid filled cysts on the surface of the liver and in the peritoneal cavity

NB: other Taenia species have muscle and brain as preferred sites in the intermediate hosts

Some can infect humans - zoonoses

Echinococcus granulosus

• Hydatid Disease
• final host
  • dog, fox, and other canids
• intermediate host
  • sheep most commonly affected
  • ox and horses

NB: can also affect man - zoonosis

• hydatids - the cyst form
  • develops from the ova
  • occur in the lung and liver
  • cysts are usually multiple
  • 5-10cm in diameter
  • contain a clear fluid with numerous scolices or "hydatid sand"
  • the small calcified lesions that are sometimes present in the liver of sheep may represent degenerate hydatid cysts
  • can be very prevalent in some geographical areas