Prevalence of Clostridium perfringens in faeces and ileal contents from grass sickness affected horses: comparisons with 3 control populations.
Authors: Waggett B E, McGorum B C, Wernery U, Shaw D J, Pirie R S
Journal: Equine veterinary journal
Summary
# Editorial Summary Equine grass sickness (EGS) has long been associated with *Clostridium botulinum* colonisation, yet the role of other pathogenic anaerobes in disease aetiology remains poorly characterised; this research investigated whether *Clostridium perfringens* might similarly be implicated. Faecal and ileal samples from EGS-affected horses were analysed using both selective culture and enzyme-linked immunosorbent assay (ELISA) and compared against three control populations: healthy grazing horses, animals with non-gastrointestinal disease, and horses with colic and co-grazing contacts. *C. perfringens* was significantly more prevalent in EGS horses than controls—detected in 41% of faecal samples from EGS cases versus just 1–2% of healthy grazing controls (P<0.001)—with similar patterns observed in ileal contents. The ELISA demonstrated excellent specificity (98%) and good positive predictive value (94%) when differentiating EGS from colic cases, though sensitivity was limited at 41%. For practitioners, these findings suggest faecal ELISA testing for *C. perfringens* could provide diagnostic support in distinguishing EGS from primary colic, particularly when clinical presentation is ambiguous; however, negative results should not exclude EGS given the test's poor sensitivity. The mechanism underlying *C. perfringens* involvement—whether pathogenic colonisation or opportunistic overgrowth secondary to neurological dysfunction—requires further investigation before the test can be considered a definitive diagnostic tool.
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Practical Takeaways
- •Faecal C. perfringens ELISA testing may help differentiate EGS from colic cases in clinical practice, particularly as a rule-in tool due to high specificity, but negative results do not exclude EGS
- •The strong association between C. perfringens and EGS suggests this pathogen may play a role in disease pathogenesis and warrants further investigation into its contribution to neuromuscular dysfunction
- •While ELISA is more practical than culture for clinical settings, the moderate sensitivity means it should be used alongside clinical signs and other diagnostic methods rather than as a standalone test
Key Findings
- •C. perfringens prevalence in faeces was significantly higher in EGS horses (41% by ELISA) compared to healthy grazing controls (1.4% by ELISA, P<0.001)
- •ELISA detection of faecal C. perfringens showed good specificity (93%) and positive predictive value (94%) for differentiating EGS from colic cases, but poor sensitivity (41%)
- •C. perfringens prevalence in ileal contents from EGS horses (50%) was nearly 5-fold higher than in horses with non-gastrointestinal disease (8.3%, P=0.056)
- •Commercial ELISA for faecal C. perfringens detection had 86% sensitivity and 98% specificity compared to culture methods