Skin Diseases

By William C. Rebhun.

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 a group develops the problem, many calves usually are affected. The causative agent generally is Trichophyton verrucosum, a fungus that lives on the skin of cattle and other livestock.

The signs of ringworm are hair loss and development of heavy gray-white crusts at the site of infection. 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 roughly circular and usually 1 to 10 centimeters in diameter.

Calves commonly are 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.

Spread of ringworm occurs through body contact and inanimate objects such as brushes or blankets used on an infected animal and then used on other animals. This problem can be transmitted to humans very easily and 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 cattle, a physician should be contacted for appropriate treatment.

Treatment is difficult because of the multiple sites and large number of animals that tend to be affected. For an individual animal, the crusts can be carefully removed and topical applications of iodine, chlorox, captan, or thiabendazole applied.

For widespread lesions or multiple animal problems, captan sprays, oral griseofulvin, or other preparations may be used. It is best to consult with a veterinarian if the problem is widespread.

Fortunately, the disease tends to be self-limiting, and affected animals usually recover spontaneously within several months. Vitamins A and D sometimes are administered as empiric treatment, and sunlight is felt to be helpful in resolving the problem.

Because of the risk of contagion, affected animals usually are not allowed to be shown in cattle shows.

Warts And Calves

Warts, or fibropapillomas, are benign skin tumors that tend to occur in calves between 4 to 24 months of age. The tumors are caused by infection of the skin with the bovine papilloma virus.

These are contagious through direct contact especially at sites of skin abrasion or injury. The virus also can be inoculated into the skin by dehorners, castration devices, and eartags which have been contaminated by affected animals.

Usual signs include raised growths that have a gray appearance and are covered by a crust. Warts usually are 1 to 10 centimeters in diameter. A calf rarely will develop "atypical warts," which are large, very numerous, and tend to affect large areas of the body. Warts tend to occur on the face, head, eyelids, ear, neck, and topline.

These warts are not contagious to people and tend to resolve spontaneously over a course of several months in affected calves and heifers. There is no specific treatment, but large warts can be removed surgically.

Wart bacterins or vaccines are used sometimes in an attempt to prevent the disease or speed resolution of the problem, but the results are variable. These vaccines should be discussed with a veterinarian if a high incidence of warts exists on a farm.

Again, as in ringworm, the contagious nature of this problem may preclude moving affected animals to shows.

Mange Problems

Cattle mange is caused by mange mites of four major types. In general, mange causes loss of hair and tremendous itching due to movement of these tiny parasites within the skin layers.

Chorioptic mange or "tail mange" is probably the most commonly recognized clinical problem and causes loss of hair over the tailhead, escutcheon, and rear udder attachment, itchiness, skin crustiness, treading of the feet, and decreased production due to the irritating nature of the disorder. This parasite also may affect horses, sheep and goats, although the signs are somewhat different than those seen in cattle.

Sarcoptic mange, or barn itch, causes a severe, generalized loss of hair, reddening of the skin, and profound itching. Affected animals lose condition dramatically and decrease in production due to the irritation and itching caused by the parasites. The parasite can affect other species of livestock, such as horses, sheep, pigs, and goats, as well as people.

Psoroptic mange causes an itchy, crusty dermatitis on the neck, withers, and tail-head of affected cattle. The dermatitis can become generalized in some instances. This type mange tends to be species specific and, therefore, the cattle psoroptic mange mite does not usually spread to other species.

Demodectic mange tends to be the most innocuous of the manges affecting cattle, and it consists of nodules or pustules on the neck, shoulders, and trunk of affected cattle. It does not tend to cause itching and is of concern mainly because of possible damage to the hide of affected animals. Demodectic mange tends to be species specific, and cattle do not spread this problem to other livestock species.