Epidemiology of equine sarcoids in horses in western Canada.

Sarcoids are the most common tumor of the equine skin but only 1 study describing the epidemiology of sarcoids in Canadian horses has been published. The records of 5 veterinary diagnostic laboratories in western Canada were searched to identify submissions of sarcoids from horses. The submission records and diagnostic reports of 802 separate submissions of equine sarcoids were reviewed for age, breed, and gender of the horse and the number, location, and clinical type of sarcoid. From these records, the 307 submissions to laboratories in Saskatchewan were compared to a reference group to test for breed and gender predisposition. Based on clinical history and lesion descriptions, 5 clinical types of sarcoids were identified. Horses of various ages and 23 equine breeds were affected; donkeys were over-represented. Polymerase chain reaction (PCR) for the bovine papillomavirus (BPV) DNA was performed on formalin-fixed paraffin-embedded tissues from a stratified subset of 96 of the different clinical types; BPV2 was present in 60 of 74 (81%) for which a PCR product was obtained. Unlike other areas in the world, in western Canada, equine sarcoids are most commonly associated with BPV type 2.