Use of antimicrobials licensed for systemic administration in UK equine practice

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.

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.

Retrospective cohort.

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.

Systemic antimicrobials were prescribed to 12 538 (19.5%, 95% confidence interval [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 with those aged 5-14 years. Breed was associated with AMU, with odds of systemic and Category B AMU highest in Thoroughbreds and Thoroughbred crosses.

Convenience sample of practices may limit generalisability.

Empirical use of Category B antimicrobials remains commonplace.