THE EPIDEMIOLOGY OF SQUAMOUS CELL CARCINOMA OF THE PERINEAL REGION OF SHEEP

Abstract

A high prevalence of squamous cell carcinoma of the perineal region of ewes was detected in the wheat belt area of Western Australia. A postal survey of 80 farms was conducted in the area, seeking information on the epidemiology of the condition, based on the farmers identification of the disease, Eighty-two per cent of flocks surveyed were affected, the mean prevalence in ewes of all ages being 2.29% (range 0.12% to 4.0%). The prevalence increased with age, from 0.05% in 1- to 2-year-old ewes to 3.09% in ewes over 5 years of age. The prevalence in the population of 121,605 ewes on all farms (affected and unaffected) surveyed, was 0.93%. The majority of lesions (88.9%) involved the vulva. The tail was affected in 23.8% of cases and the perineum in 12.8%. Affected ewes were usually destroyed and were a direct financial loss. Only 2 farmers reported the condition in rams, and 5 in wethers. Causal factors were not identified, although the radical Mules operation, time of shearing, and solar radiation were implicated.