Ringworm is a superficial, highly contagious, fungal skin infection caused by keratinophilic fungi (known as dermatophytes). Trichophyton equinum is the dermatophyte most frequently responsible for ringworm in cattle. Dermatophytes produce enzymes called keratinases that break down the protective barriers of the outer layer of the cow's skin and hair, allowing itself entry to establish infection.
Ringworm is characterized by the appearance of circular areas of hair loss, scaling, and crusting. Although in can occur anywhere on the cow's body, it most often occurs on the face, legs, belly, shoulder, and chest.
Ringworm is easily transmitted, and occurs through direct or indirect contact with skin of other infected animals, insects, people, soil or fomites. The fungus has been known to survive in the environment for up to 12 months.
The incubation period for ringworm varies from several days to a couple weeks.