Abstract
Purpose::
Chronic equine recurrent uveitis (ERU) is a common cause of blindness in horses. Although the pathogenesis is immune-mediated, the role of bacterial DNA in the initiation or recurrence of ERU is unknown.
Methods::
DNA was extracted from aqueous humor (AH) and vitreous humor (VH) from normal horses and horses from Southeastern USA with confirmed, active or chronic ERU. Aqueous humor and serum was also collected and evaluated for leptospiral titers. Broad-range ribosomal RNA quantitative PCR method was used to detect bacterial DNA in AH and VH. Test sample results were compared to a standard curve of 16s ribosomal DNA ranging from 109 - 101.
Results::
Results of quantitative PCR indicated that bacterial DNA was not identified in any test (ERU) or control sample evaluated. AH leptospiral titers were negative in most non-ERU and ERU horses. Low positive levels (<1:400) were seen in < 50% of serum from ERU horses. A Goldmann-Witmer coefficient (C-value) of <1 in all cases suggested that leptopsiral-specific antibodies detected in aqueous humor were not produced intraocularly.
Conclusions::
Presence of bacterial DNA does not appear to play a direct role in the persistence or recurrence of ERU in horses from the Southeastern USA. Although ERU horses had higher incidence leptospiral titers, C-values of <1 do not support leptospira as a direct cause for ongoing uveitis. Furthermore, due to the low prevalence of positive results, the use of PCR or titers for bacteria is not a useful method for the diagnosis of ERU
Keywords: uveitis-clinical/animal model • bacterial disease • autoimmune disease