The role ofLeptospiraspp. in horses affected with recurrent uveitis in theUK

Abstract

SummaryBackgroundEquine recurrent uveitis (ERU) is a common cause of ocular pain and blindness in horses. Leptospira spp. have been commonly implicated in the pathophysiology of ERU in mainland Europe and the USA. No recent studies have been carried out in the UK, but Leptospira is reported not to be a major factor in the aetiology of ERU in the UK.ObjectivesTo establish the prevalence of Leptospira‐associated ERU in the UK and to identify the serovars involved in these cases; to compare serum vs. aqueous humour antibody levels in cases and controls in order to confirm the diagnosis of Leptospira‐associated ERU, and to assess the usefulness of serology alone as a confirmatory test for Leptospira‐associated ERU in the UK.Study designCase–control study.MethodsEyes enucleated for clinical reasons in ERU‐affected horses were collected. Blood and aqueous humour were obtained to determine antibody levels against a variety of Leptospira serovars and C‐values (aqueous humour value/serum value) were calculated. In addition, eyes, blood and aqueous humour were obtained from control cases for comparison. Histopathology was performed in all eyes to confirm uveitis in each case. Differences in seroprevalences between ERU and control cases and between Leptospira‐ and non‐Leptospira‐associated ERU cases were calculated.ResultsA total of 30 ERU and 43 control eyes were analysed. Of the ERU eyes, only two had a C‐value of >4 (prevalence of Leptospira‐associated uveitis: 6.7%). Serovars hardjo and javanica were detected. There was no difference in seroprevalence between horses with uveitis and control cases (65.5% and 41.9%, respectively; P = 0.11) or between Leptospira‐ and non‐Leptospira‐associated uveitis cases (100% and 63.0%, respectively; P = 0.52).Main limitationsThe study was limited by low case numbers. Eyes were presented at different stages of disease. The only test used to detect Leptospira was the microscopic agglutination test.Conclusions Leptospira‐associated ERU is uncommon in the UK. Serology alone may not help to definitively diagnose Leptospira‐associated uveitis in this country.

Detection of intraocular Leptospira spp. by real‐time polymerase chain reaction in horses with recurrent uveitis in Belgium

“…Infection with Leptospira spp. has been associated with ERU with variable prevalence around the world [10][11][12][13][14][15][16][17][18]. Including diagnostic tests to identify intraocular Leptospira spp.…”

“…in ERU-affected eyes is currently recommended as this might help to determine the therapeutic management [2,17,[19][20][21][22]. Blood serology alone is not a reliable test [10][11][12]. Several laboratory methods are available including culture, antibody titres by microscopic agglutination tests on serum and ocular fluids with the calculation of the Goldmann-Witmer coefficient (C-value), and real-time polymerase chain reaction (real-time PCR).…”

“…DNA in ERU horses, with positive findings ranging from 0 to 100% [10,11,[13][14][15][16]. In most studies, the diagnosis of intraocular leptospirosis relied on the results of either aqueous or vitreous humour analysis but not on both ocular media [1,10,12,[14][15][16][17][18]. No previous equine studies have included results obtained from aqueous and the matching vitreous humours.…”

Does leptospirosis cause uveitis in the UK?

“…When using a C-value >4 as evidence of Leptospiraassociated uveitis, the study by Malalana et al (2017) suggests that Leptospira does indeed cause some cases of uveitis in the UK; however, this number appears small compared with other areas of the world.…”

Highlights of recent clinically relevant papers

“…This study by Fernando Malalana and colleagues at the University of Liverpool, aimed to provide information on the role of Leptospira infection in equine recurrent uveitis (ERU) cases in the UK .…”