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Sheep health
Closantel toxicity in ewes through drinking cattle pour-on
  1. Arthur Otter,
  2. Suzi Bell,
  3. Nathan Loewenstein,
  4. John Hemingway,
  5. Toby Floyd and
  6. Mark Wessels
  1. APHA Shrewsbury, Kendal Road, Shrewsbury SY1 4HD
  2. The Depot, Shropshire Farm Vets, Hanwood, Shrewsbury SY5 8NY
  3. APHA Weybridge, Woodham Lane, Addlestone, Surrey KT15 3NB
  4. Finn Pathologists, The School House, One Eyed Lane, Weybread, Diss, Suffolk IP21 5TT
  1. e-mail: arthur.otter{at}

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A recent case of closantel toxicity was identified in a flock of 300 Suffolk cross ewes. Three of the ewes were initially found dead, while nine others in a group of 158 developed a range of vague clinical signs including loss of condition, abnormal gait, weakness and blindness. Diarrhoea was also a feature in later-affected animals.

At the time of presentation five had died while a sixth animal was euthanased for postmortem examination. No gross pathology was identified other than mild brain yellowing and slightly swollen gyri in the cerebral hemispheres. No autofluorescence was observed when the brain was viewed under UV light. Histopathology of the brain identified only mild cellular changes affecting astrocytes, endothelial cells and neurones, and in the eye there was mild pallor and rarefaction of the optic nerve. The changes excluded cerebrocortical necrosis and encephalitis, …

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