This is an overdiagnosed cause of skin disease in the horse and is most commonly confused with trauma that is usually caused by other horses.
Ringworm is not a “worm”, instead it is the common name for fungal skin infection by a certain group of fungi called Dermatophytes. It is highly transmissible horse to horse, especially through infected tack and grooming equipment.
It is more common in young horses, and in horses under intense training, stabling and management. It tends to happen more in the winter and early spring, and usually resolves during the summer. Several of the involved Dermatophytes have the potential to infect human skin. Infection in people usually appears as scaly patches of skin with flaking, reddening and peeling.
The classic appearance of this condition in horses is well defined patches of hair loss, especially around the face and trunk. The underlying skin is often pink and the edges of the patches are scaly and flaky. Similar fungal organisms also cause girth itch which travels on tack among horses. The organism is easily transmitted horse to horse on tack and human hands, and so disinfection of hands and tack is critical to prevent spread.
The incubation period is 1-4 weeks meaning that signs of infection will usually occur within that time period after infection of the skin with the organism.
Wear gloves when treating horses with presumed ringworm. Some ringworm is zoonotic, meaning that it can be transmitted to humans. Treatment involves shampooing of affected areas (where possible the whole horse) with antiseptic/antifungal shampoos. The key is 10-15 minutes of contact time with the lather. Topical and systemic antifungals are sometimes used but are usually not necessary. Disinfection of tack and equipment and isolation of affected animals are key.
Follow any shampooing with rinsing the area well with a dilute antiseptic which kills the organism. Dry well and apply a topical antiseptic cream or mix this cream with miconozole cream. This treatment is similar to other presumed skin infections. It should be repeated daily for 5 days.
If this treatment does not work, then the horse may have a different condition. Your vet can help you make this determination.
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Prognosis & Relevant Factors
In most cases, infection is self-limiting, meaning it resolves without treatment in weeks to months. The infection usually responds well to treatment, but treatment may need to be repeated in different locations on the same horse, and spreading to other horses in a stable is common.
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