Bladder worm

General description
  • Bladder worms are large cysts (look like bladders) containing the parasite Cysticercus tenuicollis
  • Cysts are typically found in the liver and in the abdominal cavity of sheep.
  • The cysts contain intermediate stages of the dog tapeworm Taenia hydatigena (the ‘false’ hydatid tapeworm of dogs).
  • Note that bladder worm does not infect or cause hydatids in humans.
  • Sheep are infected by ingesting tapeworm eggs (passed by dogs) from contaminated pastures.
Clinical signs
  • Sheep will show no clinical signs.
  • Cysts cannot be detected in live animals but are visible at abattoir meat inspection.
  • Bladder worm cysts have a thin wall, are 1-6 cm in diameter and are filled with clear fluid. Each cyst contains an immature tapeworm.
  • They occur on the liver, diaphragm and abdominal organs and tissues.
  • Before cysts are formed, the migrating stages cause bloody tracts in the liver tissue.
  • There is no effective treatment for sheep with bladder worm cysts.
  • Treatment is not necessary as the cysts cause no economic or production loss and are not a human health risk.
  • However, affected organs (and carcases) may be condemned at processing.
  • Breaking the life cycle (between farm dogs and sheep) is the key to control.
  • Monthly worming of farm dogs, restrict access to offal and uncooked sheep meat.
  • Control wild dogs.
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