(E55) Association of Borrelia burgdorferi with Cranial Nuchal Bursitis and Elevated Ospa-specific Serum Antibodies in Horses

Abstract:

Background: Borrelia burgdorferi was identified in one case of equine cranial nuchal bursitis (CNB) with elevated serum OspA antibody value, warranting further investigation.

Objectives: To determine the significance of elevated serum OspA antibodies in cases of equine CNB and its correlation with the molecular identification of B. burgdorferi in bursal tissue or synovial fluid. Additionally, to compare the histologic changes in CNB with and without detection of B. burgdorferi.
Animals: Eighteen horses from the northeastern United States with PCR-confirmed Borrelia burgdorferi-associated CNB and 15 controls with normal cranial nuchal bursa, all unvaccinated for B. burgdorferi. Eleven additional horses with histologic diagnosis of CNB and B. burgdorferi PCR were included.

Methods: Retrospective multicenter cohort study (2013-2022). Medical records from horses with a diagnosis of CNB and B. burgdorferi PCR testing on CNB tissue or synovial fluid were reviewed. Serum equine Lyme multiplex assay results were compared between these and controls using an unpaired t-test. Histologic findings in cranial nuchal bursa tissue were compared between CNB cases with and without B. burgdorferi PCR detection.

Results: Serum OspA antibody values in B. burgdorferi positive cases were significantly elevated (P < .001) in horses with CNB (n=12) compared to controls (n=15; Figure 1). Histopathology did not vary between CNB cases with and without B. burgdorferi PCR detection.

Conclusions: Increased serum OspA antibodies are associated with the presence of B. burgdorferi in the cranial nuchal bursa of horses. The role of this pathogen in equine CNB may be underestimated and targeted therapy requires investigation.