Synovial sepsis of unknown origin in the adult Thoroughbred racehorse

Abstract

Summary Background Synovial sepsis of unknown origin is a rare cause of lameness in the adult horse, and a haematogenous pathogenesis has been proposed in previous cases. Objectives To describe the features and outcome of synovial sepsis of unknown origin in adult Thoroughbred racehorses. Study design Retrospective case series. Methods Hospital records for admissions between 2005 and 2015 were reviewed to identify adult horses diagnosed with synovial sepsis of unknown origin. Presentation, clinicopathological, microbiological and diagnostic imaging findings were recorded. Treatment methods, surgical findings, complications and long‐term outcome were evaluated. Results Eleven cases were identified over the study period. Diagnosis was established from clinical examination and clinicopathologic findings, which were comparable to other aetiologies of synovial sepsis. Affected structures included synovial joints, tendon sheaths and bursae. Concurrent osteochondritis dissecans or articular cartilage lesions were evident during arthroscopic surgery in three cases. Significant intrasynovial haemorrhage was not identified. Microbial culture of synovial fluid or synovial biopsy was positive in 6/11 of cases, with all isolates being Gram‐positive cocci. Of the 6 positive microbial cultures, all isolates demonstrated in vitro sensitivity to a cephalosporin antimicrobial agent. A concurrent remote wound was present in a single case. No other potential origins of bacteraemia were identified. Treatment methods included endoscopic surgery, standing multineedle lavage, intravenous regional limb perfusion, intrasynovial medication and/or systemic antimicrobial administration. All horses survived to hospital discharge. For the 6/11 cases that raced following synovial sepsis, the median period for return to racing was 221 days. Main limitations A small study population, which was retrospectively reviewed. Conclusions Synovial sepsis of unknown origin is rare in the adult Thoroughbred racehorse and can affect a range of synovial structures. A concurrent potential source of bacteraemia is rarely identified. With appropriate management, the prognosis to return to racing is fair.

Multicenter study investigating long‐term survival after synovial lavage of contaminated and septic synovial structures in horses presented to 10 UK referral hospitals

“…Within the equine literature, epidemiological studies specifically investigating causes of contaminated synovial structures and synovial sepsis are limited to studies on iatrogenic injury [19][20][21][22][23] and idiopathic causes. 24 There has been some research into risk factors for traumatic injuries occurring in horses The duration of time between injury and admission or treatment has been previously identified by two studies to be associated with poorer outcomes; 5,7 however, in the present study this was found to have no association with long-term survival consistent with other research. 3,9,11 The reason for these differences is unknown but may be because there are multiple factors that could affect the duration of time between the injury occurring and treatment being initiated.…”

“…In this study, detailed analysis and comparisons of the known causes of injury was not possible due to the small sample sizes. Within the equine literature, epidemiological studies specifically investigating causes of contaminated synovial structures and synovial sepsis are limited to studies on iatrogenic injury 19–23 and idiopathic causes 24 . There has been some research into risk factors for traumatic injuries occurring in horses previously 22 and, similarly, in 19% of cases the cause of injury was unknown.…”

Haematogenous synovial sepsis of the digital flexor tendon sheath following contralateral limb foot abscessation in a horse

“…10 Monomicrobial, aerobic infections are the most common isolates in cases of haematogenous synovial sepsis. [11][12][13] O'Sullivan et al 2 isolated Staphylococcus intermedius from synovial fluid, consistent with bacterial species present in pathologic hoof tissue. 14 Our report documents the isolation of Bacteroides sp., a Gramnegative anaerobic bacteria.…”

Arthritis, panuveitis and hyperaesthesia associated with Borrelia afzelii infection in a warmblood gelding

“…While septic arthritis in horses is most commonly a result of penetrating traumatic injuries or iatrogenic following intrasynovial injections, idiopathic synovial sepsis typically also involving one joint has recently been described 13 18 19. In a case series involving 11 horses, the diagnosis of synovial sepsis was based on an elevated nucleated cell count, total protein and a neutrophil differential percentage of ≥80%, whereas the culture of a causative organism was successful in only 6 patients 19. In our patient, B. afzelii DNA was detected in the tarsocrural joint via PCR analysis although synovial culture yielded a negative result.…”