Clostridium difficile: prevalence in horses and environment, and antimicrobial susceptibility.
Authors: Båverud V, Gustafsson A, Franklin A, Aspán A, Gunnarsson A
Journal: Equine veterinary journal
Summary
# Clostridium difficile in Horses: Prevalence, Environmental Persistence, and Clinical Relevance Clostridium difficile–associated colitis remains a significant concern in equine practice, particularly in mature horses receiving antimicrobial therapy, yet little was known about the organism's distribution across age groups and environmental reservoirs when this study was conducted. Swedish researchers examined 777 horses alongside environmental samples (598 soil and 434 indoor surface samples) to determine C. difficile colonisation patterns, survival characteristics, and antimicrobial susceptibility across a large dataset. Among horses developing acute colitis during antibiotic treatment, 42% tested positive for C. difficile by culture with 28% confirmed toxigenic by cytotoxin B assay, whereas the organism appeared in only 6% of untreated diarrhoeic horses and zero healthy mature horses—a striking finding being that 29% of healthy foals under 14 days of age were natural carriers, with this carriage dropping sharply in older foals. The environmental survey revealed C. difficile in 11% of stud farm soil samples but only 1% of samples from mature horse farms, demonstrating toxigenic strains can survive for at least four years in faeces under natural conditions and serving as a potential reservoir. All 52 strains tested showed complete susceptibility to metronidazole (MIC ≤4 mg/l) and vancomycin (MIC ≤2 mg/l), supporting these as reliable treatment options, whilst the identification of healthy neonatal foals as natural shedders raises important biosecurity considerations for stud farms where antibiotic-exposed foals pose particular transmission risk.
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Practical Takeaways
- •Antibiotic use is a significant risk factor for C. difficile colitis in adult horses; clinicians should use narrow-spectrum antimicrobials when possible and monitor treated horses closely for diarrhoea
- •Young foals naturally colonize with C. difficile in the first two weeks of life, but this typically self-resolves; avoid unnecessary antimicrobial treatment in neonates to prevent pathogenic overgrowth
- •Environmental contamination is higher on studfarms with foals; implement enhanced hygiene protocols during foaling season to reduce transmission risk between animals
Key Findings
- •42% of horses developing acute colitis during antibiotic treatment were positive for C. difficile culture, with 28% positive for cytotoxin B
- •29% of healthy foals aged <14 days carried C. difficile, compared to 0% of healthy mature horses
- •C. difficile isolated from 11% of outdoor soil samples on studfarms versus 1% on mature horse farms (p<0.001)
- •All 52 C. difficile strains tested remained susceptible to metronidazole and vancomycin, but strains survived in equine faeces for at least 4 years