TL;DR: Ringworm is a highly contagious fungal infection that requires prompt veterinary attention to prevent it from spreading to other pets and humans in your home.
What is ringworm and what does it look like on my cat's ear?
Ringworm, or dermatophytosis, is not actually a worm but a highly contagious fungal infection of the skin, hair, and claws. On a cat's ear, it often presents as a circular patch of hair loss, crusty or scaly skin, and sometimes mild redness or inflammation.
Is ringworm in cats considered a medical emergency?
- The urgency level for a suspected ringworm lesion is Medium.
- While rarely life-threatening, it is considered urgent because it is zoonotic and can easily spread to humans and other pets.
- Prompt treatment is necessary to stop the cycle of infection and prevent widespread environmental contamination.
How does sending a photo help my veterinarian triage my cat's condition?
- Clear images allow professionals to see characteristic 'ring' shapes, the degree of hair loss, and signs of secondary bacterial infection.
- Visuals help the veterinary team prioritize your appointment based on severity.
- Professionals can provide immediate isolation advice to keep the rest of your family safe while you wait for a clinical diagnosis.
Clinical Context (Merck Veterinary Manual)
In cats, ringworm lesions commonly manifest as focal alopecia, scaling, and crusting, frequently located around the ears and face. Dermatophytosis affects the hair of the pinnae and hairs in the concave surface of the ear canal. While a Wood's lamp can aid in a tentative diagnosis by identifying apple-green fluorescence (sebum can glow yellow), definitive diagnosis requires a dermatophyte test medium (DTM) culture. Treatment involves systemic antifungal therapy, ideally in conjunction with whole-body topical treatment such as shampoos containing miconazole (with or without chlorhexidine) once or twice weekly or enilconazole (0.2% at a dilution of 1:70). Spot-on treatments alone are not recommended, as they may predispose to chronic subclinical infection.
Chapter: Dermatology
Source: The Merck Veterinary Manual, 11th Edition (Page 874)