Antibiotic usage in 14 equine practices over a 10-year period (2012-2021).

Background: Monitoring antibiotic usage is an important part of tackling antimicrobial resistance. The use of computerised records for monitoring has been previously described in the equine sector but there is currently no consensus on metrics used to report usage.

Objectives: To document antibiotic use in equine practices in the United Kingdom over a 10-year period using commercially available practice management software.

Study Design: Retrospective survey.

Methods: A custom antibiotic usage report was created using Eclipse® practice management software. Participating practices were given instructions on how to generate the usage report. Annual reports were requested for a 10-year period (2012-2021 inclusive). Each report provided sales of each class of antibiotic in total mg and in mg/kg, based on the number of equids treated (for any transaction) and their average weight. The defined daily dose for animals (DDDvet) and the DDD/1000 (used in people) were also calculated to correct for variation in dosage rates between antibiotics.

Results: Fourteen practices submitted data for an annual maximum of 107 977 horses. Overall, median annual antibiotic usage was 54.25 mg/kg (range 45.34-60.27 mg/kg), 1.52 defined daily doses/animal/year (range 1.39-1.70) and 4.17 defined daily dose/1000 animals (range 3.82-4.66). Overall median highest priority critically important antimicrobial usage was 0.67 mg/kg (range 0.56-1.71), 0.12 defined daily doses/animal/year (range 0.10-0.14) and 0.33 defined daily dose/1000 animals (range 0.29-0.39).

Main Limitations: The software relied on the accurate identification of antibiotic preparations. The calculation of DDDvet was complicated by the varying dose rates of antimicrobials used in equine practice.

Conclusions: A reliable technique to measure antibiotic usage is presented. Defined daily dosage calculations may be more helpful in equine practice due to the preponderance of potentiated sulphonamides usage. These data and methods may provide the basis for future clinical audits aiming to enhance antimicrobial stewardship.