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Vetdle Archive

Archive Case #38: Ovine Fly Strike

Sheep veterinary case - Easy - April 10, 2026

Clinical Clues

  1. A ewe is seen repeatedly biting at her rump during a period of warm humid weather.
  2. The wool over the breech is damp, matted, and discoloured.
  3. Flies are concentrated around a foul-smelling patch of fleece.
  4. On parting the wool, the underlying skin is moist, inflamed, and crawling with larvae.
  5. Nearby sheep are at risk because several have heavily soiled fleece.
  6. Warm conditions and wet contaminated wool commonly predispose sheep to cutaneous maggot infestation.

Diagnosis

Ovine Fly Strike

This case is most consistent with Ovine Fly Strike because the ewe has irritated moist fleece with maggots present beneath the wool in fly-prone conditions. The most important clues are the breech staining, foul odour, and visible larvae, which clearly distinguish this from a simple dermatitis.

Learning review

Review the case evidence

Use the paired clues to explain how the evidence in this sheep case supports the provided diagnosis, Ovine Fly Strike, then compare your reasoning with the case explanation.

Evidence checkpoints

Clues 1-2

  1. Clue 1: A ewe is seen repeatedly biting at her rump during a period of warm humid weather.
  2. Clue 2: The wool over the breech is damp, matted, and discoloured.

Clues 3-4

  1. Clue 3: Flies are concentrated around a foul-smelling patch of fleece.
  2. Clue 4: On parting the wool, the underlying skin is moist, inflamed, and crawling with larvae.

Clues 5-6

  1. Clue 5: Nearby sheep are at risk because several have heavily soiled fleece.
  2. Clue 6: Warm conditions and wet contaminated wool commonly predispose sheep to cutaneous maggot infestation.

Self-review prompts

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

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.