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Mortality, clinical findings, predisposing factors and treatment of Clostridioides difficile colitis in Japanese thoroughbred racehorses
  1. Motoi Nomura1,
  2. Taisuke Kuroda2,
  3. Norihisa Tamura2,
  4. Masanori Muranaka3 and
  5. Hidekazu Niwa4
  1. 1 The Horse Racing School, Japan Racing Association, Shiroi, Chiba, Japan
  2. 2 Clinical Science & Pathobiology Division, Equine Research Institute, Japan Racing Association, Shimotsuke, Tochigi, Japan
  3. 3 Racehorse Hospital, Miho Training Center, Japan Racing Association, Inashiki, Ibaraki, Japan
  4. 4 Microbiology Division, Equine Research Institute, Japan Racing Association, Shimotsuke, Tochigi, Japan
  1. Correspondence to Dr Motoi Nomura; Motoi_Nomura{at}


Background Although Clostridioides difficile-associated diseases (CDAD) is considered to be associated with colitis in horses, few studies have been performed with a focus on the characteristics of CDAD in thoroughbred racehorses.

Methods Between 2010 and 2018, a test for C. difficile was performed using faecal samples from 137 thoroughbred racehorses with colitis presenting with diarrhoea and fever. The mortality rate, clinical findings, predisposing factors and the selected treatments were investigated in a retrospective manner.

Results Twenty-four cases were diagnosed as CDAD and 113 as non-CDAD. The mortality rate was significantly higher in the CDAD group (83 per cent) than that in the non-CDAD group (34 per cent). The levels of serum amyloid A, blood urea nitrogen and packed cell volume at initial presentation were also significantly higher, and those of total protein and albumin were significantly lower in the CDAD group. The development of CDAD was associated with the administration of antimicrobials, surgery and hospitalisation. No significant improvement in mortality was observed for any of the selected treatment in both groups.

Conclusion CDAD in thoroughbred racehorses was identified as a high mortality disease with rapid progression of systemic inflammation and deterioration of the circulatory state. Further investigation is required to improve the treatment.

  • Clostridioides difficile
  • colitis
  • thoroughbred
  • diarrhoea
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  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data availability statement Data are available on reasonable request. Datasets used and/or analysed during the current study are available from the corresponding author on reasonable request. Please contact corresponding author: Motoi Nomura (

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