Ringworm (Dermatophytosis) in Horses

Dermatophytosis is a common condition in horses that is typically mild, but can spread quickly within a herd if not treated. It can be painful or itchy. Veterinary attention is required to differentiate dermatophytosis from other serious skin conditions such as rain scald or folliculitis, as dermatophytosis can infect humans.

Horses that are infected with dermatophytosis are not permitted in competitions or races, in certain locations, or to travel across borders. Follow up tests are sometimes necessary to prove that treatment has been effective if the hair has not grown back before a horse is expected to compete or travel.

The severity of dermatophytosis depends on to what extent it has spread over the body.

In mild cases of dermatophytosis, very few, small spots of hair loss and rash are present. In moderate cases, larger patches develop, often in a cluster. Horses with severe dermatophytosis have large areas of inflammation in several places on their bodies.

In some cases, patches of ringworm are painful or itchy. Scratching against objects creates further damage to the skin that allows further development and continued spread of the condition to other horses.

Young and elderly horses, as well as horses who are in poor health, are more susceptible to dermatophytosis. The fungal spores are more commonly found in the autumn and winter months.

Horses that share tack, grooming equipment, stalls, trailers, or handlers with infected horses are at a higher risk. Fences, walls, and other surfaces that are in contact with infected horses can also carry the fungus. The spores are also found in the soil. Horses living in moist conditions for long periods of time are also at a higher risk.

Dermatophytosis is a fungal infection of the skin, typically caused by Microsporum and Trichophyton species of fungus in horses. These fungi are very hardy and can survive in the environment for a long time, which means that they are easily transmitted through direct contact with an infected horse or by contact with contaminated materials or surfaces.

Typically, the skin protects the body from infection. When the skin is broken or waterlogged, ringworm fungi can make their way into the lower layers of the skin where they thrive.

Symptoms are often found in roughly ring-shaped patterns on the skin.

Dermatophytosis typically resolves on its own within 6 to 12 weeks. Horses still benefit from veterinary examination to confirm the diagnosis, particularly since the fungus can affect humans. Diagnosis is based on physical examination, skin scrapes, and hair samples.

Treatment is recommended, even though it does not necessarily shorten the duration of the infection. Appropriate treatment limits the severity of the symptoms and reduces the risk of transmission to other horses or people. For small areas of dermatophytosis, treatment involves medicated creams. For larger infections, medicated baths are required. It is necessary to clip the hair and remove the scabs and other debris from the skin before applying topical medications in order to ensure contact between the medications and the fungus. People treating horses with dermatophytosis must wear gloves to prevent the infection from spreading to themselves.

In severe cases and where more than one horse is infected in a herd, oral medications are available.

With or without treatment, the condition usually takes between 6 and 12 weeks to resolve. Horses with mild or moderate infections have an excellent prognosis. Horses with severe infections have a more guarded prognosis.

Once symptoms have resolved, lost hair takes 1 to 4 weeks to grow back.

Dermatophytosis is very contagious. Preventing transmission requires infected horses to be isolated for at least 3 weeks. Since the symptoms take between 4 and 30 days to develop, new horses being introduced to the stable should be isolated for a few weeks to see if symptoms develop.

Once dermatophytosis is present, diligence about hygiene is necessary to stop it from spreading to other animals and humans. Strategies include:

• Avoiding sharing tack, grooming tools, and other equipment between horses
• Disinfecting tack, grooming tools, and other equipment when they must be shared
• Disinfecting stalls and trailers between uses by different horses
• Burning old bedding and clipped hair from infected horses
• Using antimicrobial sprays and disinfectants on shared spaces
• Washing fabric items such as blankets and leads twice before using them on uninfected horses
• Avoiding sharing equipment used to treat infected horses, such as sponges or buckets
• Disposing of equipment used to treat infected horses once treatment is complete
• Handling infected horses last

Dermatophytosis is common in horses.

• Medicated creams
• Medicated baths
• Oral medications
• Quarantine protocols
• Environmental decontamination