Equine Thrush Study Guide

Overview and Clinical Importance

Thrush is a degenerative, keratolytic condition of the equine frog caused primarily by Fusobacterium necrophorum, an anaerobic, gram-negative bacterium. This opportunistic infection affects the central and collateral sulci of the frog, producing characteristic black, foul-smelling discharge and potentially causing lameness if the condition extends to dermal tissues.

Thrush is one of the most commonly encountered hoof conditions in equine practice and represents a significant category on the NAVLE. Understanding the etiology, predisposing factors, clinical presentation, differential diagnosis (particularly from canker), and appropriate treatment protocols is essential for examination success and clinical competence.

Etiology and Pathophysiology

Causative Agent

The primary pathogen associated with equine thrush is Fusobacterium necrophorum, an obligate anaerobic, gram-negative, pleomorphic rod bacterium. Research by Petrov and Dicks (2013) confirmed that F. necrophorum, and not Dichelobacter nodosus (the agent involved in ovine and bovine foot rot), is the causative agent in equine thrush.