Warts (infectious papillomatosis) are caused by papilloma viruses. In cattle at least 6 distinct strains of papilloma viruses have been recognised, each producing characteristic lesions. The virus is transmitted by direct contact, contaminated objects (e.g. equipment), and possibly by insects, with the virus gaining entry through skin abrasions or wounds.

Multiple papillomas (papillomatosis) of the skin or mucosal surfaces are most commonly seen in younger animals. Single papillomas are more frequent in older animals, but they may not always be caused by viral infection.

Clinical signs

The incubation period—that is, the time a wart takes to develop after infection—is normally around 8 weeks but can be longer. Warts may last for up to twelve months or more before spontaneously regressing.

In cattle, warts commonly occur on the head, neck and shoulders, but can be found anywhere on the body. The extent and duration of the lesions depend on the type of virus, area affected, and degree of susceptibility, with young cattle under 2 years of age being most susceptible. Papillomatosis becomes a herd problem when the infection occurs in a large group of young, susceptible cattle. Immunity usually develops 3–4 weeks after initial infection, which persists for at least 2 years.

Warts are usually small with a cauliflower-like appearance and cause little trouble. Occasionally, warts may infect large areas of the body and cause ill-thrift if they interfere with normal function or become infected or flyblown through trauma. Some types of warts may involve the venereal regions where they can cause pain, disfigurement, infection of the penis of young bulls, and dystocia when the vaginal mucosa of heifers is affected.

Control and treatment

Infectious papillomatosis should generally be regarded as a self-limiting disease, although the duration of warts varies considerably. In most cases lesions disappear as immunity develops and should be left alone.

If warts persist and/or require removal then surgical removal is recommended. Depending on the size and extent of the lesions, this may be by surgical resection, ligation if pedunculated (on a stalk), cryosurgery or thermocautery.

There are no commercially availble vaccines for the prevention of warts. Autogenous wart vaccines made from warts removed from the affected animal, may be useful for the treatment of extensive wart lesions. Various wart ointments are available with varying effectiveness. Consult your vet for advice.

Affected animals may be isolated from susceptible ones to reduce the chance of spread, but with the long incubation period, many are likely to have been exposed before the problem is recognised. Mustering, yarding, dipping and other husbandry practices should be kept to a minimum during any noticeable outbreak of warts to avoid stress.