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Vetdle Archive

Archive Case #89: Equine Grass Sickness

Horse veterinary case - Hard - May 31, 2026

Clinical Clues

  1. A horse on pasture develops dullness, reduced appetite, and patchy sweating.
  2. The owner reports small amounts of dry faeces and a tucked-up abdomen.
  3. There is mild colic behaviour, but the pattern is not typical of an acute surgical lesion.
  4. The horse has rhinitis sicca and difficulty prehending feed.
  5. Clinical findings indicate widespread autonomic dysfunction.
  6. This often-fatal neuropathy of grazing horses is known as equine grass sickness.

Diagnosis

Equine Grass Sickness

This case is most consistent with Equine Grass Sickness because the horse shows gastrointestinal stasis, autonomic dysfunction, and characteristic dysphagia-related signs while at pasture. The most important clues are the dry faeces, rhinitis sicca, and autonomic picture, which make ordinary colic far less likely.

Learning review

Review the case evidence

Use the paired clues to explain how the evidence in this horse case supports the provided diagnosis, Equine Grass Sickness, then compare your reasoning with the case explanation.

Evidence checkpoints

Clues 1-2

  1. Clue 1: A horse on pasture develops dullness, reduced appetite, and patchy sweating.
  2. Clue 2: The owner reports small amounts of dry faeces and a tucked-up abdomen.

Clues 3-4

  1. Clue 3: There is mild colic behaviour, but the pattern is not typical of an acute surgical lesion.
  2. Clue 4: The horse has rhinitis sicca and difficulty prehending feed.

Clues 5-6

  1. Clue 5: Clinical findings indicate widespread autonomic dysfunction.
  2. Clue 6: This often-fatal neuropathy of grazing horses is known as equine grass sickness.

Self-review prompts

  1. After clues 1-2, what evidence from this horse case shaped your initial interpretation?
  2. When you compare clues 3-4 with clues 1-2, what changed in your reasoning about Equine Grass Sickness?
  3. How do clues 5-6 align with the case explanation for Equine Grass Sickness?

Educational Use

Vetdle archive cases are educational veterinary games for diagnostic reasoning practice. They do not provide veterinary advice, diagnosis, treatment, or professional medical guidance.