Antimicrobial-associated diarrhoea in three equine referral practices.
Authors: Barr B S, Waldridge B M, Morresey P R, Reed S M, Clark C, Belgrave R, Donecker J M, Weigel D J
Journal: Equine veterinary journal
Summary
# Antimicrobial-Associated Diarrhoea in Equine Practice Antimicrobial-associated diarrhoea (AAD) represents a significant post-treatment complication in horses, yet robust epidemiological data remain limited. Researchers across three equine referral hospitals reviewed their 2009 caseloads to establish prevalence rates and identify which antimicrobials posed the greatest risk, examining all non-hospitalised horses aged weanling and older that developed diarrhoea after treatment for non-gastrointestinal conditions. Among 5251 horses receiving antimicrobials for non-gastrointestinal reasons, 32 were diagnosed with probable AAD (0.6% prevalence), though this subset experienced concerning outcomes: 18.8% mortality, an average treatment duration of only 4.2 days before onset, and identification of Clostridium difficile in four cases and Salmonella in three. Gentamicin-penicillin combinations, enrofloxacin, and doxycycline dominated the AAD cases, demonstrating that risk spans all antimicrobial classes rather than concentrating in particular drugs. Whilst the absolute prevalence is reassuringly low, these findings underscore the importance of judicious antimicrobial prescribing and highlight that opportunistic enteropathogens may act synergistically with treatment to trigger clinical disease—information that should inform clinicians' choice of agent, duration, and monitoring protocols, particularly in higher-risk patients.
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Practical Takeaways
- •While AAD risk is low (0.6%), it carries significant mortality (18.8%), so prudent antimicrobial stewardship is essential in equine practice
- •Any antimicrobial class can potentially cause AAD; monitor for diarrhoea during treatment and ensure appropriate duration of therapy
- •Consider opportunistic enteropathogens when diarrhoea develops post-antimicrobial treatment; faecal pathogen testing may identify treatable secondary infections
Key Findings
- •AAD prevalence was 0.6% (32/5251) in horses treated with antimicrobials for non-gastrointestinal conditions
- •Mortality rate in AAD cases was 18.8% (6/32 horses)
- •Most common antimicrobials associated with AAD were gentamicin-penicillin combinations (n=7), enrofloxacin (n=7), and doxycycline (n=4)
- •Clostridium difficile was identified in 4 horses with AAD, with 50% mortality, and Salmonella in 3 horses