Occurrence and severity of equine recurrent uveitis in warmblood horses - A comparative study

Abstract

About 10% of horses in Germany suffer from equine recurrent uveitis (ERU). In the present study we have compared varying degrees of ERU-associated clinical signs with special regard to the horse's colour, age, gender and uni- or bilateral affection. Furthermore we have investigated a possible correlation between severity of clinical signs and detection of leptospiral antigens and antibodies in the vitreous humor of horses after surgery. Horses with other diseases than ERU served as controls (n = 4955). They were patients in the Clinic for Horses of the University of Veterinary Medicine Hannover, Foundation, between April 2010 and November 2011. The ERU-diagnosed group consisted of 119 horses, in which we scored the severity in each eye. In 44 of those horses a double-port pars plana vitrectomy was performed in 51 eyes. The obtained material was tested for antibodies against varying leptospiral serovars. ERU was diagnosed more frequently in male horses, which is consistent with findings in male human patients with an ERU-comparable HLA-B-27-associated uveitis anterior. Additionally, we could demonstrate that horses with brown and black coat colour were significantly more often affected with ERU than other colours. Our data do not indicate a correlation between age and the occurrence of ERU. Regarding uni- or bilateral ERU, we found that out of 157 examined eyes 31% were left, 37% were right and 32% were bilaterally affected. In the bilaterally affected horses there was a significant correlation with higher age. However, there was no correlation between higher age and severity score. By testing the vitreous humor after surgery in 45 eyes, 49% (n=22) of the probes were positive for leptospiral antibodies (in 87% antibodies against the serovar Grippotyphosa) and leptospiral DNA was detected in 20 eyes. In 1 7 eyes (38%) antibodies as well as antigen were detected. As a result, we counted 26 of the examined 51 eyes (56%) as positive for leptospires. Those eyes were scored higher (Score 3 to 5) compared to leptospires-negative eyes (Score 1 to 2).