Dermatophytosis (ringworm) is a superficial fungal skin disease of cattle. The most common clinical signs include crusting, scaling, and focal areas of hair loss. Pruritus is variable. Definitive diagnosis is made via fungal culture; however, diagnosis via clinical signs is not uncommon. Infected animals may or may not be treated because dermatophytosis is self-limiting. Topical treatment is the only cost-effective treatment.
Trichophyton verrucosum is the usual cause of dermatophytosis in cattle, but T mentagrophytes, T equinum, Nannizzia gypsea (formerly Microsporum gypseum), M nanum, M canis, and others have also 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 typically develop lesions on the chest and limbs, while bulls generally develop lesions in the dewlap and intermaxillary skin.
Lesions are characteristically discrete, scaly, alopecic patches with gray-white crusts (see image of dermatophyte infection, cow), but some become thickly crusted and suppurated. Dermatophytosis as a herd health problem is more common in winter when animals are housed in close quarters more frequently and is more commonly recognized in temperate climates.
Courtesy of Dr. Karen A. Moriello.
Treating cattle with oral antifungal medications is not cost-effective. Treatment involves improvement of husbandry because overcrowding increases disease prevalence. Remove crusts with a brush, discard the brush, and burn the infective material. Topical therapy, with lime sulfur 1:16 or enilconazole 1:100 leave-on rinses, is the treatment of choice. Do not use bleach, which can be irritating and is a human health hazard. Twice-a-week treatment is recommended if this is practical. Continue treatment until lesions resolve and no new lesions develop.
As in other animals, dermatophytosis will self-cure in cattle.
A live, attenuated fungal vaccine is in use in some countries, although it is not available in North America. In control and eradication programs, the vaccine prevents both development of clinical lesions and transmission to other animals and has decreased the number of new infected herds. Vaccination can also decrease the incidence of zoonotic disease in farmers and their household members, veterinarians, and workers in slaughterhouses and tanneries.
For More Information
White S. Food Animal Dermatology: Part 1. World Association for Veterinary Dermatology webinar.
White S. Food Animal Dermatology: Part 2. World Association for Veterinary Dermatology webinar.
Guarnieri E, Sauve F. Bovine dermatology: how to approach skin diseases in this species. Can Vet J. 2022;63(9):973-978.
