Risk factors for a first episode of primary uveitis in the UK and proportion of cases that experience recurrence following this first episode
Malalana, F. et al (2022) Risk factors for a first episode of primary uveitis in the UK and proportion of cases that experience recurrence following this first episode. Equine Veterinary Journal.
This prospective, case-control longitudinal study aimed to determine the potential risk factors for the development of primary uveitis in horses in the UK and the prevalence of cases that experience recurrence following this first episode.
The study was carried out between 2014-2018 at a UK university equine hospital. Horses with primary uveitis were recruited for the study; for each case, two control horses with no history of ocular disease were recruited. At enrolment, owners completed a questionnaire on their horse, giving initial data on signalment, history, management, and clinical signs. Thereafter, follow-ups with veterinary surgeons and case owners were carried out every six months for reports of recurrent clinical signs of the disease six weeks after the resolution of the original episode.
A total of 23 cases and 46 controls were recruited to the study; one case was lost to follow-up. The results showed that development of primary uveitis was significantly associated with time spent by horses on premises close to a pig farm or in a field with a recent history of flooding. In contrast, the risk of developing uveitis decreased for every year the horse spent with the same owner.
5/22 (22.7%) cases could not be resolved medically and required surgical management. Recurrence occurred in 4/22 (18.2%) cases. For three of these cases, recurrence happened after three months and in the fourth case after 12 months.
Limitations of the study include the small number of cases, possible selection bias of cases and controls by the referring veterinary surgeons and the potential recall bias from the owners. The study population was geographically restricted so it may not be generalisable to other equine populations in the UK.
This study suggests that horses living close to pig farms or grazing in pastures that have recently flooded may be more likely to develop uveitis. This information will help veterinary surgeons identify horses that may be at risk and advise owners accordingly. The low number of cases that experienced recurrence provides some information which could inform discussions on prognosis with owners.
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