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Veterinary ophthalmology2026; 29(1); e70132; doi: 10.1111/vop.70132

Evaluation of Laboratory Techniques for the Diagnosis of Leptospira-Associated Equine Recurrent Uveitis (ERU) With Focus on the Goldmann-Witmer Coefficient.

Abstract: To evaluate different laboratory procedures for determining the etiologic diagnosis of equine recurrent uveitis regarding intraocular infection with Leptospira spp. and to establish a diagnostic guideline. Methods: Eighty horses with a history of ERU were ophthalmologically examined. Serum and aqueous humor were collected. Total protein, albumin level, and MAT against Leptospira spp. were evaluated on serum and aqueous humor. PCR for Leptospira spp., EHV-1 and -4 was performed on aqueous humor. Goldmann-Witmer coefficient (GWC) and C-value (CC) were calculated based on MAT. In 42 cases, an additional ELISA was initiated. Results: Forty-six female and 34 male horses of different breeds (mean age 10.9 years; range 3 to 31) were included. By MAT 56/80 horses (70.0%) were identified seropositive for Leptospira spp. MAT results were positive for Leptospira spp. in aqueous humor of 47/80 (58.8%) patients. PCR tested 16/80 (20.0%) positive, ELISA detected 13/42 (31.0%) positive. Neither EHV-1 nor EHV-4 were detected by PCR. Calculating GWC gives evidence suggestive of intraocular involvement with Leptospira spp. in 53/80 (66.3%) at the level ≥ 3. Setting GWC ≥ 3 as gold standard, ELISA and C ≥ 2 closely matched this threshold, showing high accuracy (95.2%; 91.3%), sensitivity (86.7%; 84.9%), and strong agreement (V = 0.90; V = 0.81). PCR was less accurate (53.8%) and sensitive (30.2%) compared to GWC. Conclusions: Within this setting, GWC achieved the highest number of positive results for detecting intraocular involvement of Leptospira spp. when compared to PCR, ELISA, and C-value.
© 2026 The Author(s). Veterinary Ophthalmology published by Wiley Periodicals LLC on behalf of American College of Veterinary Ophthalmologists.
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Publication Date: 2026-01-10 PubMed ID: 41518147PubMed Central: PMC12790138DOI: 10.1111/vop.70132Google Scholar: Lookup
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  • Journal Article

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Overview

  • This study evaluated various laboratory diagnostic methods to detect intraocular infection with Leptospira bacteria in horses suffering from Equine Recurrent Uveitis (ERU).
  • The Goldmann-Witmer Coefficient (GWC) was assessed alongside other tests to establish which method is most effective for identifying Leptospira-associated ERU.

Background

  • Equine Recurrent Uveitis (ERU) is a common eye disease in horses that causes repeated inflammation of the uveal tract and often leads to blindness.
  • A significant cause of ERU is believed to be infection with Leptospira spp., a type of bacteria.
  • Detecting intraocular infection accurately is crucial for effective diagnosis and treatment.
  • Various laboratory techniques exist to diagnose Leptospira-associated ERU, but their relative effectiveness had not been firmly established.

Study Objectives

  • To compare multiple laboratory methods for diagnosing Leptospira infection of the eye in horses with ERU.
  • To focus on evaluating the Goldmann-Witmer Coefficient (GWC) and its utility compared to other diagnostic tests.
  • To develop guidelines for reliable etiological diagnosis of Leptospira-associated ERU.

Methods

  • Sample Size and Subjects:
    • 80 horses with a history of ERU were included (46 female, 34 male, various breeds).
    • Mean age was approximately 11 years, ranging from 3 to 31 years old.
  • Sample Collection:
    • Ophthalmological examination was performed on all subjects.
    • Both serum (blood) and aqueous humor (fluid from inside the eye) samples were collected.
  • Laboratory Tests Conducted:
    • Microscopic Agglutination Test (MAT) against Leptospira spp. on serum and aqueous humor to look for antibodies.
    • Measurement of total protein and albumin levels in serum and aqueous humor to assess blood-ocular barrier integrity.
    • Polymerase Chain Reaction (PCR) tests on aqueous humor to detect DNA of Leptospira spp. and Equine Herpesvirus types 1 and 4 (EHV-1 and EHV-4).
    • Goldmann-Witmer Coefficient (GWC) and C-value (CC) calculations based on MAT results to assess local antibody production in the eye.
    • An ELISA antibody test was additionally performed in 42 of the horses for comparison with other tests.

Key Findings

  • Seropositivity:
    • 70% (56/80) of horses tested positive for Leptospira antibodies in serum via MAT.
    • 58.8% (47/80) showed positive MAT results for Leptospira in aqueous humor.
  • PCR Results:
    • Only 20% (16/80) were PCR-positive for Leptospira DNA in aqueous humor.
    • None of the samples were positive for EHV-1 or EHV-4 by PCR.
  • ELISA Results:
    • In the subset of 42 horses tested, 31% were ELISA-positive for Leptospira antibodies in the eye fluid.
  • Goldmann-Witmer Coefficient (GWC):
    • Suggestive intraocular involvement was found in 66.3% (53/80) at a threshold GWC ≥ 3.
    • GWC identified more positive cases compared to PCR and ELISA.
  • Diagnostic Performance:
    • When using GWC ≥ 3 as the gold standard:
      • ELISA and C-value with threshold ≥ 2 showed high accuracy (95.2% and 91.3%) and sensitivity (86.7% and 84.9%).
      • Strong agreement was observed between GWC and ELISA (V = 0.90) and between GWC and C-value (V = 0.81).
      • PCR demonstrated lower accuracy (53.8%) and sensitivity (30.2%), indicating it was less effective at detecting intraocular Leptospira infection compared to antibody-based tests.

Conclusions and Clinical Implications

  • The Goldmann-Witmer Coefficient (GWC) was the most sensitive and effective test for diagnosing intraocular Leptospira infection in horses with ERU in this study.
  • Compared to PCR, which detects bacterial DNA, antibody detection methods (GWC, ELISA, C-value, MAT) performed better, likely because antibodies persist and are more abundant than bacterial DNA in the eye fluid.
  • GWC and related measurements provide a useful diagnostic guideline for veterinarians assessing Leptospira involvement in ERU, aiding targeted treatment decisions.
  • Testing for EHV-1 and EHV-4 by PCR was negative, suggesting these viruses are not common causes of intraocular inflammation in ERU cases studied.

Summary

  • This study highlights the importance of antibody-based diagnostics, especially the Goldmann-Witmer Coefficient, to identify intraocular Leptospira infection in horses with ERU.
  • Results support use of GWC as a gold standard reference to guide diagnosis and treatment.
  • The findings help clarify which laboratory methods are most reliable for equine uveitis diagnosis related to leptospiral infection.

Cite This Article

APA
Kirmse L, Thieme K, Doherr MG, Eule JC. (2026). Evaluation of Laboratory Techniques for the Diagnosis of Leptospira-Associated Equine Recurrent Uveitis (ERU) With Focus on the Goldmann-Witmer Coefficient. Vet Ophthalmol, 29(1), e70132. https://doi.org/10.1111/vop.70132

Publication

Veterinary ophthalmology
ISSN: 1463-5224
NlmUniqueID: 100887377
Country: England
Language: English
Volume: 29
Issue: 1
Pages: e70132
PII: e70132

Researcher Affiliations

Kirmse, Lena
  • Ophthalmology Unit, Centre for Veterinary Clinical Services, Freie Universität Berlin, Berlin, Germany.
  • Tierärztliche Praxis für Pferde Stefanie Süß, Deinste, Lower Saxony, Germany.
Thieme, Katharina
  • Equine Clinic Seeburg, Dallgow-Döberitz, Germany.
Doherr, Marcus Georg
  • Institute of Veterinary Epidemiology and Biostatistics, School of Veterinary Medicine, Freie Universität Berlin, Berlin, Germany.
Eule, Johanna Corinna
  • Ophthalmology Unit, Centre for Veterinary Clinical Services, Freie Universität Berlin, Berlin, Germany.

MeSH Terms

  • Animals
  • Horses
  • Horse Diseases / diagnosis
  • Horse Diseases / microbiology
  • Leptospirosis / veterinary
  • Leptospirosis / diagnosis
  • Uveitis / veterinary
  • Uveitis / diagnosis
  • Uveitis / microbiology
  • Female
  • Leptospira / isolation & purification
  • Male
  • Aqueous Humor / microbiology
  • Enzyme-Linked Immunosorbent Assay / veterinary
  • Polymerase Chain Reaction / veterinary

Grant Funding

  • Dahlem Research School and Elsa-Neumann-Stipendium

Conflict of Interest Statement

The authors have not used AI to generate any part of the manuscript. The authors declare no conflicts of interest.

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