Veterinarian Cornell University Ithaca, NY, United States
Abstract: Background - Nuchal bursitis is an uncommon, challenging cause of pain and decreased performance in horses. Radiographic identification of mineralization within the nuchal bursa and/or ligament is often considered incidental in the absence of swelling and pain. Recently, cases of nuchal bursitis associated with Borrelia burgdorferi infection have been reported. Hypothesis/Objectives - To investigate the incidence of subclinical nuchal bursitis, characterize its histopathologic features and association with Borrelia burgdorferi. Animals - Fifteen horses, 4-29 years old, (5 geldings, 10 mares, various breeds). Methods - Prospective descriptive cadaver study on a convenient population of horses in a B. burgdorferi endemic region. Research horses undergoing euthanasia and tissue donation without history or clinical signs of nuchal bursitis. Cranial nuchal bursa, synovial fluid and nuchal ligament were collected post-mortem. The bursa and ligament were evaluated via histopathology scoring system, grading inflammation, edema, fibrosis, and mineralization (0-normal to 18-severe). Lyme Multiplex assay on serum and Borrelia burgdorferi PCR on bursa were performed. Results – Gross abnormalities were found in four horses (calcification, abscess, synovial effusion, adhesions). On histopathology, lymphoplasmacytic and lymphohistiocytic inflammation was detected in four horses. Six horses showed other mild changes (edema, fibrosis, mineralization). The overall histopathology score ranged from 1 to 7 (mean 2±1.65). Five horses had positive Lyme Multiplex assay antibody titers. All tissue samples were negative on B. burgdorferi PCR. Conclusion and Clinical Importance - Our study suggests a high incidence of mild/moderate nuchal bursa and ligament histopathologic changes (67%), warranting further investigation of their causes and clinical implications.
