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.
Cause
- Sheep are infected by ingesting tapeworm eggs (passed by dogs) from contaminated pastures.
Clinical signs
- Sheep will show no clinical signs.
Diagnosis
- 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.
Treatment
- 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.
Prevention
- 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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