Long-term results of pars plana vitrectomy in relationship to leptospiral antibody detection in vitreous humor in 118 horses with equine recurrent uveitis (ERU)

In the ongoing discussion regarding aetiopathogenesis and therapeutic approach of equine recurrent uveitis (ERU) it was the aim of the present study to elucidate the relationship of leptospiral antibody detection in vitreous humor and success of pars plana vitrectomy (PPV) in horses with ERU. In a retrospective study of 118 ERU patients of different age, gender and breed undiluted vitreous humor, aseptically taken at the beginning of PPV, was examined by culture. Furthermore vitreous humor and serum were tested for specific antibodies against different serovars of Leptospira interrogans by microscopic agglutination test (MAT). Horses were treated via single port pars plana vitrectomy. The presence or absence of inflammation of the inner eye 8 to 54 months after PPV was evaluated by repeated ocular examinations, as well as by interrogation of referring veterinarians and horse owners. The absence of recurrent inflammation in terms of symptoms of classic uveitis after surgery was considered a success. A total of 55 of 118 horses (46.6%) had serum antibodies against different serovars of Leptospira (L.) interrogans (1 : 100). Culture of vitreous humor was positive in 16/118 (13.6%) patients with ERU. In 49 of 118 horses (41.5%) and 52 of 134 eyes (38.8%) leptospiral antibodies were detected in vitreous humor via MAT. L. interrogans serovar Grippotyphosa (48) and L. interrogans serovar Pomona (12) were identified most frequently. A total of 90/118 (76.3%) horses and 104/134 eyes (77.6%) remained relapse-free over a period of 8 to 54 months. Forty-one/49 horses (83.7%) and 44/52 eyes (84.6%), tested positive for antibodies against L. interrogans via MAT and 49/69 horses (71.0%) and 60/82 eyes (73.2%), in which no leptospiral antibodies were detected in vitreous humor, showed no further episodes of ERU (Fishers exact test: P.0.05). These findings confirm the therapeutic approach to perform a vitrectomy according to the clinical ERU diagnosis irrespective of the leptospiral antibody result.