Serum and vitreous humor antibody titers in and isolation of Leptospira interrogans from horses with recurrent uveitis

Objective-To measure antibody titers against Leptospira interrogans in seru m and vitreous humor and determine the prevalence of Leptospira interrogans in vitreous humor of horses with recurrent uveitis. Design-Cross-sectional study. Animals-242 horses (270 eyes) with recurrent uveitis undergoing vitrectomy and 39 control horses (54 eyes) without any history or clinical signs of re current uveitis undergoing euthanasia or enucleation for unrelated reasons. Procedure-Serum and vitreous humor were tested for antibodies against 13 se rovars of L interrogans. Vitreous humor was submitted for leptospiral cultu re; isolates were typed to the serogroup level. Results-Leptospira interrogans was isolated from vitreous humor from 120/22 9 (52%) horses (126/252 [50%] eyes) with recurrent uveitis but was not isol ated from vitreous humor from 36 eyes of 21 control horses. Duration of rec urrent uveitis was greater than or equal to1 year for 45 of the 120 (38%) h orses from which the organism was isolated. Geometric mean antibody titers against L interrogans in the vitreous humor and serum of horses with recurr ent uveitis were 1:1,332 and 1:186, respectively. Only 91 of 120 (76%) hors es from which the organism was isolated had a 4-fold or greater difference between serum and vitreous humor antibody titers. Conclusions and Clinical Relevance-Results suggest that persistent ocular i nfection with L interrogans is common in horses with recurrent uveitis. A 4 -fold increase in vitreous humor versus serum antibody titers may not be a sensitive test for the diagnosis of L interrogans-induced recurrent uveitis . We hypothesize that the immune component of recurrent uveitis can be dire ctly induced and maintained by persistent infection of the eye with L inter rogans.