Role of bacteria in the pathogenesis of recurrent uveitis in horses from the southeastern United States

Objective—To determine the role of intraocular bacteria in the pathogenesis of equine recurrent uveitis (ERU) in horses from the southeastern United States by evaluating affected eyes of horses with ERU for bacterial DNA and intraocular production of antibodies against Leptospira spp. Sample Population—Aqueous humor, vitreous humor, and serum samples of 24 clinically normal horses, 52 horses with ERU, and 17 horses with ocular inflammation not associated with ERU (ie, non-ERU inflammation). Procedures—Ribosomal RNA quantitative PCR (real-time PCR) assay was used to detect bacterial DNA in aqueous humor and vitreous humor from clinically normal horses (n = 12) and horses with chronic (> 3-month) ERU (28). Aqueous humor and serum were also evaluated for anti-Leptospira antibody titers from clinically normal horses (n = 12), horses with non-ERU inflammation (17), and horses with confirmed chronic ERU (24). Results—Bacterial DNA was not detected in aqueous humor or vitreous humor of horses with ERU or clinically normal horses. No significant difference was found in titers of anti-Leptospira antibodies in serum or aqueous humor among these 3 groups. Only 2 horses, 1 horse with ERU and 1 horse with non-ERU inflammation, had definitive intraocular production of antibodies against Leptospira organisms. Conclusions and Clinical Relevance—In horses from the southeastern United States, Leptospira organisms may have helped initiate ERU in some, but the continued presence of the organisms did not play a direct role in the pathogenesis of this recurrent disease.