Pathology and diagnostic criteria of Clostridium difficile enteric infection in horses.
Authors: Diab S S, Rodriguez-Bertos A, Uzal F A
Journal: Veterinary pathology
Summary
# Editorial Summary: *Clostridium difficile* Pathology in Horses Whilst *C. difficile*-associated diarrhoea is well documented clinically in horses, detailed descriptions of the actual tissue damage it causes have been limited, prompting this 2013 pathological examination of 21 horses with confirmed *C. difficile* infection. The researchers identified cases using toxin detection (ELISA) for *C. difficile* A/B toxins combined with compatible gross and microscopic intestinal findings, then systematically documented the characteristic lesions across the gastrointestinal tract. Grossly, affected horses displayed multifocal to diffuse haemorrhage, congestion, and gelatinous oedema of the intestinal wall alongside haemorrhagic or green watery intestinal contents; microscopically, severe necrotising or necrohemorrhagic inflammation dominated, particularly in the colon and caecum, frequently accompanied by mucosal and submucosal thrombosis and marked oedema. The critical finding is that *C. difficile* pathology in horses closely resembles that caused by other enteric pathogens, meaning clinical signs and gross lesions alone are insufficient for diagnosis—toxin detection in intestinal contents remains essential for definitive confirmation. This highlights the importance of pursuing specific diagnostic testing rather than relying on clinical presentation or post-mortem appearance when *C. difficile* is suspected, particularly in cases of severe haemorrhagic colitis where treatment decisions and infection control protocols depend on accurate identification.
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Practical Takeaways
- •Gross and microscopic lesions of C. difficile colitis in horses are non-specific and resemble other enteric infections; toxin detection (ELISA) is essential for definitive diagnosis
- •Expect severe hemorrhagic colitis with marked edema and thrombosis on necropsy or biopsy of horses suspected of CDAD
- •Diagnosis cannot be made on pathology alone—always pair histology with C. difficile toxin detection in intestinal samples for accurate diagnosis
Key Findings
- •Gross pathology included multifocal to diffuse hemorrhage, congestion, and marked gelatinous edema of intestinal walls with bloody or green watery contents in 21 horses with CDAD
- •Histologically, severe necrotizing or necrohemorrhagic enteritis/colitis/typhlocolitis with mucosal/submucosal thrombosis and marked submucosal edema were the most common lesions
- •Pathologic features of equine CDAD are similar to other enteric pathogens, making definitive diagnosis dependent on C. difficile A/B toxin detection in intestinal contents via ELISA