Peer-reviewed veterinary case report
Presumptive Lyme disease-associated eosinophilic synovitis in a horse.
- Journal:
- Journal of equine veterinary science
- Year:
- 2025
- Authors:
- Serpa, P B S et al.
- Affiliation:
- Department of Biomedical Sciences and Pathobiology · United States
- Species:
- horse
Plain-English summary
A 1-year-old American Quarter horse was brought in because she suddenly started limping on her right hind leg. The vet found fluid buildup in her right hock joint, and tests showed a type of inflammation called eosinophilic synovitis, which involves certain white blood cells. Blood tests suggested she had both recent and past infections with a bacteria called Borrelia burgdorferi, which is linked to Lyme disease, but tests on the joint fluid didn’t confirm it. She was treated with medications and showed improvement, but after eight months, she had lameness again with fluid in both hock joints. Further tests showed a different type of inflammation, and after completing another round of antibiotics, she fully recovered. This case suggests that the horse had a unique inflammatory condition possibly related to the Lyme disease bacteria.
Abstract
A 1-year-old American Quarter horse was presented with acute onset of right hind lameness. On physical examination, there was synovial effusion of the right tarsocrural joint. Synovial fluid cytology revealed a marked eosinophilic synovitis. Serology indicated evidence of acute and chronic infection with Borrelia burgdorferi, although PCR of the synovial fluid was negative. The filly was treated with phenylbutazone and oxytetracycline, and repeated synovial cytology indicated improvement. The filly was discharged with a prescription of minocycline for 30 days. Despite initial improvement, recurrent lameness with bilateral tarsocrural effusion without radiographic abnormalities occurred 8 months later. Repeated synovial cytology showed macrophagic synovitis without an eosinophilic component. The filly was discharged with instructions to complete a 14-day course of minocycline, resulting in complete recovery. Based on the serology results and response to therapy, this report describes a possible naturally occurring eosinophilic synovitis with likely involvement of B. burgdorferi, a condition previously unreported in horses.
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Search related cases →Original publication: https://pubmed.ncbi.nlm.nih.gov/40339728/