Use of antimicrobials licensed for systemic administration in UK equine practice.

BACKGROUND: Judicious antimicrobial use (AMU) is important for preserving therapeutic effectiveness. Large-scale studies of antimicrobial prescribing can provide clinical benchmarks and help identify opportunities for improved stewardship.

OBJECTIVES: To describe systemic AMU in UK equine practice and identify factors associated with systemic and Category B (third and fourth generation cephalosporins, quinolones and polymixins) AMU.

STUDY DESIGN: Retrospective cohort.

METHODS: Anonymised electronic patient records (EPRs) for all equids attended by 39 UK veterinary practices between 1 January and 31 December 2018 were collected via the VetCompass™ programme. Systemic antimicrobial prescriptions were identified using electronic keyword searches. Indications for AMU were determined through manual review of a randomly selected subset of EPRs. The types and frequency of systemic antimicrobials prescribed and indications were summarised using descriptive statistics. Mixed-effects logistic regression was used to evaluate practice- and horse-related risk factors.

RESULTS: Systemic antimicrobials were prescribed to 12,538 (19.5%, 95% CI 19.2-19.8%) of 64,322 equids attended in 2018. Category B antimicrobials were prescribed to 1.9% (95% CI 1.8-2.0%) of attended equids and in 8.9% (95% CI 8.5-9.4%) of antimicrobial courses. Bacteriological culture was performed in 19.1% (95% CI 17.1-21.3%) of Category B antimicrobial courses. The most commonly prescribed antimicrobial classes were potentiated sulphonamides (50.2% of equids receiving antimicrobials) and tetracyclines (33.5% of equids receiving antimicrobials). Integumentary disorders were the most common reason for systemic AMU (40.5% of courses). Urogenital disorders were the most common reason for Category B AMU (31.1% of courses). Increased odds of systemic and Category B AMU were observed in equids <1 year compared to those aged 5-14 years. Breed was associated with AMU, with odds of systemic and Category B AMU highest in Thoroughbreds and Thoroughbred crosses.

MAIN LIMITATIONS: Convenience sample of practices may limit generalisability.

CONCLUSIONS: Empirical use of Category B antimicrobials remains commonplace.