Ringworm in Dogs and Cats: Identifying and Treating Fungal Skin Infections
Ringworm is a contagious fungal infection that affects the skin, hair, and claws of pets — and it can spread to humans too. Here's what you need to know.
Despite its name, ringworm is not caused by a worm — it's a fungal infection of the skin, hair, and claws. The name comes from the circular, ring-like pattern of hair loss that appears on infected animals. Ringworm is highly contagious between pets and can also spread to humans (zoonotic). In Macau's warm, humid climate, ringworm spores can survive in the environment for months, making treatment and prevention especially important.
Key Points
- Ringworm is caused by fungi called dermatophytes, not worms
- It's highly contagious between pets and can spread to humans
- Circular patches of hair loss with flaky, red skin are classic signs
- Cats often carry ringworm without showing obvious symptoms
- Treatment requires antifungal medication for 6-8+ weeks minimum
- Environmental decontamination is essential to prevent reinfection
What Causes Ringworm?
Ringworm is caused by a group of fungi called dermatophytes that feed on keratin — the protein found in skin, hair, and nails. The most common species in pets is Microsporum canis, responsible for about 70% of cases in dogs and 98% in cats. Other species include Microsporum gypseum and Trichophyton mentagrophytes. The fungi produce microscopic spores that can survive in the environment for 12-18 months. Infection occurs through direct contact with an infected animal or contact with contaminated objects like bedding, grooming tools, or furniture.
Signs and Symptoms
The classic sign is circular patches of hair loss with a red, scaly, or crusty border — the 'ring' pattern. In dogs, lesions typically appear on the face, ears, paws, and tail. In cats, signs can be subtle — some cats are asymptomatic carriers, while others develop patchy hair loss, broken hairs, and dandruff-like scaling. The claws can also be infected, becoming rough, brittle, and deformed. Kittens, puppies, senior pets, and animals with compromised immune systems are most susceptible. The infection can be itchy or completely non-itchy depending on the individual.
Diagnosis and Treatment
Your vet can diagnose ringworm using several methods: a Wood's lamp (ultraviolet light) causes some ringworm species to glow fluorescent green; a microscopic examination of plucked hairs (fungal culture is the gold standard but takes 10-14 days); or PCR testing for faster results. Treatment typically includes: topical antifungal creams (miconazole, clotrimazole) or medicated shampoos (chlorhexidine/miconazole combination), and oral antifungal medication (terbinafine or itraconazole) for more widespread infections. Treatment must continue for at least 6-8 weeks and past the point of apparent cure, as determined by follow-up testing.
Environmental Decontamination
Ringworm spores survive in the environment for months, so cleaning is essential. Vacuum all carpets and upholstery daily (discard vacuum bags immediately). Wash all bedding, blankets, and soft toys in hot water with bleach. Disinfect hard surfaces with diluted bleach (1:10 solution) or commercial antifungal cleaners. Restrict your pet to rooms that are easy to clean. Treat all pets in the household — even those without symptoms. Be aware that ringworm can spread to humans, especially children, the elderly, and immunocompromised individuals. If anyone in the family develops circular, red, itchy skin patches, see a doctor.
When to See a Vet Immediately
- You notice circular patches of hair loss on your pet
- Your pet has flaky, scaly, or crusty skin that doesn't improve
- You see broken or damaged hairs in patchy areas
- Your pet's claws become rough, brittle, or misshapen
- Multiple pets in your household are developing skin issues
- Family members have developed circular, red, itchy skin patches
How RVC Can Help
RVC can diagnose ringworm through Wood's lamp examination, fungal culture, and PCR testing. We offer comprehensive treatment plans including oral antifungal medications, medicated shampoos, and guidance on environmental decontamination. Our team will help you manage this contagious infection safely for your whole household. Call +853 6677 6611.
This article is for educational purposes only and does not replace professional veterinary advice. If your pet is showing any symptoms, please contact Royal Veterinary Center immediately at +853 6677 6611.