The role of Leptospira spp. in horses affected with recurrent uveitis in the UK.
BACKGROUND
Equine 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.


OBJECTIVE
To 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.


METHODS
Case-control study.


METHODS
Eyes 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.


RESULTS
A 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).


CONCLUSIONS
The 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.
School of Veterinary Science, University of Liverpool, Neston, UK.
F
http://orcid.org/0000-0002-5773-9725
F
Malalana
School of Veterinary Science, University of Liverpool, Neston, UK.
R J
RJ
Blundell
Institute of Infection and Global Health, School of Veterinary Science, University of Liverpool, Neston, UK.
G L
GL
Pinchbeck
Institute of Ageing and Chronic Disease, School of Veterinary Science, University of Liverpool, Neston, UK.
C M
CM
Mcgowan
D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D001082:Aqueous Humor / Q000382:microbiology; D006734:Horse Diseases / Q000097:blood / Q000453:epidemiology / Q000382:microbiology*; D006736:Horses; D007919:Leptospira / Q000145:classification / Q000302:isolation & purification*; D007922:Leptospirosis / Q000150:complications / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*; D006113:United Kingdom / Q000453:epidemiology; D014605:Uveitis / Q000097:blood / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary*
D000907:Antibodies, Bacterial

ERU
; antibody titre; aqueous humour; horse; seroprevalence