Equine Aural Plaques Study Guide

Overview and Clinical Importance

Aural plaques (also known as papillary acanthoma, pinnal acanthosis, or hyperplastic aural dermatitis) are a common, benign papillomavirus-induced skin condition affecting the inner surface of the equine pinna. These lesions are characterized by well-demarcated, depigmented, hyperkeratotic plaques that rarely spontaneously resolve. While typically asymptomatic and primarily a cosmetic concern, aural plaques can cause significant ear sensitivity and behavioral issues in affected horses, making this a frequently tested topic on the NAVLE.

The clinical prevalence of aural plaques in horses is significant, with studies demonstrating that at least 22% of horses are affected, and some regional studies in Brazil have found prevalence rates as high as 14.8% among examined populations. Understanding the etiology, clinical presentation, and management of this condition is essential for veterinary practice and board examination success.

Etiology and Pathogenesis

Causative Agent

Aural plaques are caused by infection with Equus caballus papillomavirus (EcPV). Multiple viral types have been identified in association with aural plaques, with EcPV types 3, 4, 5, and 6 being most commonly detected. Recent molecular studies have demonstrated that EcPV-4 is the most prevalent type, found in up to 84% of affected horses, followed by EcPV-3, EcPV-6, and EcPV-1. Coinfection with multiple EcPV types is common, occurring in approximately 59% of cases.