Canine Dermatophytosis Study Guide

Overview and Clinical Importance

Dermatophytosis (commonly known as ringworm) is a superficial fungal infection affecting the skin, hair, and occasionally claws of dogs. Despite its name, this condition is not caused by a worm but by keratinophilic fungi belonging to the genera Microsporum, Trichophyton, and Epidermophyton. Understanding dermatophytosis is essential for the NAVLE examination due to its zoonotic potential, clinical significance in shelter medicine, and the importance of accurate diagnosis.

Dermatophytosis represents less than 4% of all canine skin disorders, yet it is frequently over-diagnosed clinically due to its classic appearance that can mimic staphylococcal pyoderma. A common clinical adage states: "If it looks like ringworm in a dog, it's probably staphylococcal pyoderma."

Etiology

Primary Causative Agents

Three main dermatophyte species cause the vast majority of canine infections. Understanding their relative prevalence, sources, and characteristics is high-yield for the NAVLE.