Equine Pigeon Fever Study Guide

Overview and Clinical Importance

Pigeon fever, also known as dryland distemper or false strangles, is an infectious disease of horses caused by the Gram-positive bacterium Corynebacterium pseudotuberculosis biovar equi. The disease derives its name from the characteristic swelling in the pectoral muscles that gives affected horses a "pigeon-breasted" appearance. This condition represents an important infectious disease on the NAVLE examination due to its increasing geographic distribution, distinctive clinical presentations, and specific treatment considerations.

Historically endemic to the southwestern United States and California, pigeon fever has expanded significantly over the past two decades with outbreaks reported in states that had not previously documented cases. The disease primarily occurs during late summer and fall months, correlating with peak fly activity, though cases can occur year-round. Understanding the three clinical forms, diagnostic approaches, and treatment protocols is essential for board examination success.

Etiology

Causative Agent

Corynebacterium pseudotuberculosis is a Gram-positive, pleomorphic, rod-shaped, facultatively anaerobic, intracellular bacterium. Key microbiological characteristics include: