Warts are hairless, normally benign growths on skin or mucosa caused by a papilloma virus. The virus enters skin and mucosal abrasions after direct contact with infected animals, and fomites such as contaminated feed troughs, ear tagging pliers and rectal palpation sleeves. The papilloma viruses causing warts in cattle do not cause warts in humans.
Typically, the condition affects young adult cattle under two years old. Lesions appear suddenly and proliferate rapidly. The disease is self limiting, but the timing of regression is unpredictable and ranges from one month to over one year. Animals with warts should be excluded from the export process if they are likely to become the subject of negotiations during health inspection at destination. Warts reduce value of hides and may bleed, become infected or flyblown, and affect reproduction if they occur on penis and prepuce of bulls, or the udder and vulva of cows.
Warts can occur anywhere on the body including the oesophageal groove and reticulum, but they are most frequently seen on surfaces prone to abrasion such as the head (especially around the eyes, ears and lips), neck, shoulder and brisket. They vary in form and size from 1 mm diameter to large, broad-based masses hanging from the neck or brisket. Warts have a hard surface, may be smooth and rounded, or have finger-like projections, or have a rough cauliflower appearance. They may have a dry or crusty surface.
Laboratory confirmation requires a biopsy specimen submitted in buffered formalin for histology.
Differential diagnoses include chronic ringworm, dermatophilosis, cutaneous lymphosarcoma, solar keratosis and squamous cell carcinoma.
Treatment of warts is rarely necessary. In most cases it is best to let the disease run its course. Surgical removal of large, awkwardly located or ulcerated warts is sometimes necessary. However, removal may be followed by recurrence or stimulation of growth. Ligation of pedunculated warts may effect removal. Autogenous vaccines have been used to treat warts but effectiveness is uncertain because self cure is common.
Autogenous vaccines and anti-viral compounds/disinfectants can be used to control the disease in problem herds. Vaccination must commence at a very young age. Infected animals may be isolated from herd mates, but the long incubation period means other animals are likely to have been exposed. The virus is enduring in the environment - premises and equipment may remain infected for over one year.