LAUSR

BACKGROUND Risk factors for a first episode of primary uveitis in horses have not been determined. In addition, disease progression and the proportion of horses that develop recurrence following the original episode is not known. OBJECTIVES To determine risk factors for the development of a first episode of primary uveitis in horses in the UK and to document the proportion of cases that experience recurrence following this first episode. STUDY DESIGN Prospective case-control longitudinal study. METHODS Horses with a first episode of primary uveitis between July 2014 and August 2018 were recruited to the study. For each case, two controls were selected. A questionnaire was completed for each horse and multivariable logistic regression analysis carried out to identify associations between horse and management-level variables and the risk of uveitis. Each case was then followed longitudinally to determine the rate of recurrence of uveitis. RESULTS 23 cases and 46 controls were recruited. Being close to a pig farm (OR 27.8, CI 1.31-592.06) and a recent history of flooding of the pasture (OR 15.43, CI 2.80-84.98) were associated with increased risk of uveitis. Being in the same owner's possession for a longer amount of time had a protective effect (OR 0.79, CI 0.68-0.93). Horses recovered uneventfully following treatment and showed no evidence of recurrence in 59.1% of the cases (n=13). In five horses (22.7%) the initial episode of uveitis could not be controlled and required surgical therapy. Recurrence was observed in four horses (18.2%). MAIN LIMITATIONS Small sample size. Recall bias from owners for some of the data. Possibility of selection bias. CONCLUSIONS Clinicians can use this information to identify horses with increased risk of uveitis and provide advice to the owners of these horses. The proportion of cases that experience recurrence appears low in the UK.