Evaluation of breed as a risk factor for sarcoid and uveitis in horses.

The relationship between breed and the risk of developing sarcoid tumours or uveitis of unknown etiology was evaluated in a retrospective study of 16242 equine cases admitted between 1975 and 1987 to the New York State College of Veterinary Medicine Large Animal Hospital, and 3198 equine tissue samples sent to the New York State Veterinary Diagnostic Laboratory between 1977 and 1987. Of 120 sarcoid cases from the Large Animal Hospital, sarcoids were twice as likely to develop in Quarter Horses (odds ratio, OR = 1.8, P less than 0.05) relative to Thoroughbreds and less than half as likely to develop in Standardbreds (OR = 0.2, P less than 0.001) relative to Thoroughbreds. Similarly, of 376 sarcoid cases from the Diagnostic Laboratory, Quarter Horses had a significantly higher risk of developing sarcoid (OR = 2.0, P less than 0.001) relative to Thoroughbreds, while Standardbreds had a significantly lower risk of developing sarcoid (OR = 0.5, P less than 0.05) relative to Thoroughbreds. In the uveitis diagnosis category, Appaloosas had a significantly higher risk of developing uveitis (OR = 6.4, P less than 0.001) relative to Thoroughbreds, while Standardbreds had a significantly lower risk of developing uveitis (OR = 0.4, P less than 0.05) relative to Thoroughbreds.