Uveitis is a leading cause of blindness in horses. Little work has been undertaken to investigate whether donkeys are affected by a similar disease prevalence.
To investigate the disease prevalence of uveitis in a population of donkeys in the UK.
Descriptive observational study.
An ophthalmic examination was performed on each donkey, in a darkened stable. Each donkey underwent slit lamp biomicroscopy, and direct and/or indirect ophthalmoscopy. Fluorescein staining, STT1 and IOPs were measured when deemed clinically necessary. Pharmacological pupillary dilation was achieved using 1% tropicamide.
A total of 207 donkeys were examined-139 male (67.1%), and 68 female (32.9%). Age range was 2-37 years (median 17 years, inter-quartile range 9-25 years). Three donkeys (1.5%) were blind in one eye, and one was monocular at the time of examination. Signs consistent with either previous or current uveitis were identified in 8 eyes of 6 animals (2.9%). Clinical signs included: miosis (n=1), corpora nigra atrophy (n=6), anterior lens capsule pigment (n=2), cataract (n=8), posterior synechiae (n=3), lens subluxation (n=1), vitreal changes (n=2), peripapillary scarring (n=3), and phthisis bulbi (n=1). Significant ocular pathology precluded fundic examination in 3 eyes. Three out of eight eyes (37.5%) were blinded by the pathology. The risk of uveitis was found to increase with age (OR 1.1, CI 1.01-1.25) on univariable analysis (p=0.05).
Fluorescein staining, tonometry and Schirmer Tear Test measurements were not performed on all donkeys.
The disease prevalence reported here is comparable to that reported for horses in the UK. Larger prospective studies are necessary, to determine if there is a similar trend in disease prevalence in the donkey population worldwide. In addition, further investigations should aim to establish if uveitis in donkeys is similar to the ERU syndrome seen in horses.
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