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Archive Case #195: Equine Rhodococcus Equi Pneumonia

Horse veterinary case - Medium - September 14, 2026

Clinical Clues

  1. Fever, cough, and steadily increasing respiratory effort develop in a young foal.
  2. Over the same period, the foal falls noticeably behind its peers in growth.
  3. Thoracic auscultation suggests lower airway involvement rather than an upper respiratory problem.
  4. Ultrasound identifies peripheral pulmonary abscessation.
  5. Tracheobronchial aspirate cytology shows septic airway inflammation in a foal with ultrasonographic lung abscesses.
  6. Culture plus PCR amplification of the vapA gene from the tracheobronchial aspirate confirms virulent Rhodococcus equi pneumonia.

Diagnosis

Equine Rhodococcus Equi Pneumonia

This case is most consistent with Equine Rhodococcus Equi Pneumonia because the foal has chronic lower respiratory disease with pulmonary abscessation on farm conditions that favour Rhodococcus equi. The most important clues are the age and abscessing pneumonia pattern, which make a simple viral respiratory infection 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 Rhodococcus Equi Pneumonia, then compare your reasoning with the case explanation.

Evidence checkpoints

Clues 1-2

  1. Clue 1: Fever, cough, and steadily increasing respiratory effort develop in a young foal.
  2. Clue 2: Over the same period, the foal falls noticeably behind its peers in growth.

Clues 3-4

  1. Clue 3: Thoracic auscultation suggests lower airway involvement rather than an upper respiratory problem.
  2. Clue 4: Ultrasound identifies peripheral pulmonary abscessation.

Clues 5-6

  1. Clue 5: Tracheobronchial aspirate cytology shows septic airway inflammation in a foal with ultrasonographic lung abscesses.
  2. Clue 6: Culture plus PCR amplification of the vapA gene from the tracheobronchial aspirate confirms virulent Rhodococcus equi pneumonia.

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 Rhodococcus Equi Pneumonia?
  3. How do clues 5-6 align with the case explanation for Equine Rhodococcus Equi Pneumonia?

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.