Originally written by Tracey Erickson, former SDSU Extension Dairy Field Specialist.
As County and State Fairs roll around, we prepare our animals for the show ring. This process involves a health check and obtaining a certificate of veterinary inspection (health papers) from a veterinarian prior to exhibition. A common problem in animals is ringworm, which can bring a show season to a screeching halt. Ringworm can be found in cats, dogs, sheep, rabbits, dairy and beef cattle, and horses.
Ringworm is a fungal infection of the skin (dermatomycosis) that occurs commonly in calves and occasionally in adult cattle. It is contagious, therefore, when one calf in the group develops the problem, many calves usually are affected. The causative agent is Trichophyton verrucosum, a spore forming fungus that lives on the skin of cattle and other livestock.
In checking your animal for ringworm you should look for hair loss in a circular pattern and development of heavy, gray-white crusts and redness at the site of infection. The lesion will appear to spread outward. There may be one or several lesions present on an animal. The lesions do not cause itching. If the crusts are scraped or cleared away, a raw area of skin devoid of hair is found. The lesions are usually one to ten centimeters in diameter. Calves are commonly affected in several spots around the face, eyelids, ears, and neck, although lesions can occur anywhere on the body. Adult cattle, when affected, tend to have more generalized lesions on the face, neck, trunk, and tail region.
The spread of ringworm occurs through body contact of an infected animal or through inanimate objects such as brushes, clippers, combs, clipping chutes, halters, blankets, fences or buildings. Preventing the spread from one animal to the next involves not sharing of these items between animals or disinfecting between each animal. The fungus can survive in barns and livestock pens which should also be disinfected with a strong detergent followed by a 1:3 dilution of bleach and water. Cleaning show tack, feed buckets, pails, and grooming equipment with either a bleach solution followed by proper oiling and maintenance of all leather and grooming equipment is an important step in ringworm prevention. Additional helpful prevention measures include reduction of stocking density in pens and increased exposure to sunlight and maintenance of dry lots or pens.
Ringworm is a zoonotic disease which means transmission to humans can easily happen. Therefore it is an important public health problem for farm workers and veterinarians that handle affected animals. If ringworm is suspected in a human who has been in contact with infected cattle, a physician should be contacted for appropriate treatment.
Often mild lesions are spot treated with antifungal creams. However, if the case is more severe it is best to consult with your veterinarian to get the approved treatment methods and to get the problem cleared up before show time. Remember, it may take several weeks to clear the problem up, so plan ahead. You should remember that those animals that are infected with ringworm are unable to be shown until the ringworm is healed.