Trichophyton verrucosum is the usual cause of ringworm in cattle, but T mentagrophytes, T equinum, Microsporum gypseum, M nanum, M canis, and others have been isolated. Dermatophytosis is most commonly recognized in calves, in which nonpruritic periocular lesions are most characteristic, although generalized skin disease may develop. Cows and heifers develop lesions on the chest and limbs, and bulls develop lesions in the dewlap and intermaxillary skin. Lesions are characteristically discrete, scaling patches of hair loss with gray-white crust formation, but some become thickly crusted with suppuration. Dermatophytosis as a herd health problem is more common in the winter and is more commonly recognized in temperate climates.
It is not cost effective to treat cattle with oral antifungal medications. Treatment involves improvement of husbandry because overcrowding increases disease prevalence. Remove crusts with a brush and discard the brush and burn the infective material. Topical therapy is the treatment of choice, with lime sulfur 1:16 or enilconazole 1:100leave-on rinses. Do not use bleach, because this can be irritating and a human health hazard. Twice-a-week treatment is recommended if this is practical. Dermatophytosis will self cure in animals.
A live-attenuated fungal vaccine is in use in some countries; it is not available in North America. The vaccine has been used in control and eradication programs to successfully decrease the number of new infected herds. The vaccine prevents development of clinical lesions and transmission to other animals. Vaccination can reduce the incidence of zoonotic disease in farmers, their households, veterinarians, and people working in slaughterhouses and tanneries.