What is Ringworm (Dermatophytosis)?

Dermatophytosis is an infection of the skin or hair caused by a type of fungus. Trichophyton equinum and T mentagraphytes are the primary causes of ringworm in horses, although Microsporum gypseum, M canis, and T verrucosum have also been isolated. 

Clinical Signs: Clinical signs of ringworm often start as a circular eruption followed by crusts, hair loss (alopecia) and inflammation (erythema). The amount of inflammation is dependent on the pathogen. 

Diagnosis: Diagnosis can be rapidly confirmed by direct microscopic examination of hairs and scales or by fungal culture. Lesions should not be wiped with alcohol, because this can cause a negative culture. Early lesions should be sampled and provided to a reference laboratory, along with scales, hairs and crusts. 

Treatment: The treatment of choice is twice weekly, whole body, leave-on rinses with lime sulfur 1:16 or enilconazole 1:100. Adjuvant topical treatment on non-rinse days can be used. Effective products include enilconazole in a spray form (stable for 7 days) or a spray formulation of 2% chlorhexidine/1% ketoconazole or 2% chlorhexidine/1%–2% miconazole. Lesions around the eyes can be treated with 1%–2% miconazole vaginal cream once daily. Infected animals should be isolated. Tack should be thoroughly cleaned by first removing gross organic debris and then washing thoroughly with a detergent soap. Disinfection can be accomplished with any over-the-counter bathroom cleaner labeled as antifungal for Trichophyton spp. Fabric leads or blankets should be washed twice in a washing machine. 

Prevention:  Routine treatment of tack and grooming are the primary methods of prevention.