The overuse of antimicrobials in companion animals is a significant concern due to its contribution to the development, carriage, and transmission of antimicrobial resistance (AMR). Companion animals, living in close proximity to humans, can act as reservoirs for AMR bacteria, particularly when high-priority critically important antimicrobials (HPCIAs) like cefovecin (a 3rd-generation cephalosporin) and fluoroquinolones are frequently prescribed. While some encouraging trends in antimicrobial reduction have been observed in recent population studies utilizing electronic health records (EHRs), antimicrobials remain commonly prescribed. The frequent prescription of HPCIAs, ideally reserved for human use, often lacks clear clinical justification. Studies using EHRs have identified various factors influencing antimicrobial prescription, including animal characteristics, owner behavior, clinical presentation, individual veterinary surgeon practices, and the overall culture of veterinary practices. Significant inter-practice variation in HPCIA prescription has been noted. Interventions aimed at improving antimicrobial prescription, such as evidence-based prescribing guidance and practice benchmarking, have shown limited impact. There is a perceived lack of knowledge among veterinary surgeons regarding relative frequencies of antimicrobial prescriptions, leading to the hypothesis that benchmarking (drawing attention to individual deviation from a social norm) may reduce over-prescription. This study presents a randomized controlled trial that evaluates the efficacy of social norm messaging, EHR-driven antimicrobial prescription benchmarking, and in-practice educational support to significantly reduce HPCIA prescription frequency.

The literature review highlights the growing concern of antimicrobial resistance (AMR) in companion animals and its link to human health. Studies show a strong correlation between frequent antimicrobial use in companion animals and the spread of AMR bacteria. Cefovecin, a third-generation cephalosporin classified as a highest priority critically important antimicrobial (HPCIA) by the World Health Organization (WHO), is particularly prevalent in feline prescriptions, often without sufficient clinical justification. Existing research reveals considerable inter-practice variation in antimicrobial prescribing, suggesting a need for effective interventions. While guidelines and benchmarking have been suggested, robust evidence supporting their effectiveness is lacking. Qualitative studies have explored the multifaceted factors influencing antimicrobial prescribing behaviors, including animal and owner characteristics, clinical presentations, individual veterinarian practices, and the broader practice culture. These studies underscore the complex interplay of factors requiring a multi-pronged approach to address the issue.

This three-armed randomized controlled trial (RCT) utilized data from 157 veterinary practices within the CVS Group Ltd. participating in the Small Animal Veterinary Surveillance Network (SAVSNET). The study period spanned from August 2018 to November 2019. Sixty practices with above-average HPCIA prescribing rates were randomly allocated to three groups: a control group (CG, n=20), a light intervention group (LIG, n=20), and a heavy intervention group (HIG, n=20). The primary outcome measure was post-intervention HPCIA prescription frequency. Baseline characteristics of practices, including staff numbers and consultation types, were collected and compared across groups. The LIG received a letter and email notifying them of their above-average HPCIA prescribing and providing access to educational materials and an online benchmarking portal. The HIG received the same materials as the LIG, plus an in-depth benchmarking report and the option to participate in a reflection and education program facilitated by hub clinical leads. The intervention involved initial notification (March 2019), followed by an eight-month post-intervention monitoring period (April-November 2019). The HIG practices had access to additional support (follow-up meetings) for the first six months. Data analysis included mixed-effects panel regression models to compare HPCIA prescription frequencies across groups, pre- and post-intervention, considering various factors such as species, main presenting complaint, and time. Antimicrobial prescription choice, anti-inflammatory prescription frequency, euthanasia rates, and diagnostic test frequencies were also analyzed.

The HIG demonstrated significant reductions in canine (23.5%, P=0.04) and feline (39.0%, P<0.001) HPCIA prescribing consultations compared to the CG. The LIG showed a significant 16.7% reduction in feline HPCIA prescriptions (P=0.03). Post-intervention, the HIG experienced a significant 18.9% reduction in systemic antimicrobial prescriptions in dogs and a 17.3% reduction in cats compared to the CG. The HIG's month-by-month analysis revealed significant reductions in HPCIA prescription in three months for dogs and eight months for cats. There were notable decreases in HPCIA prescribing within specific main presenting complaints (MPCs) in both species. Portal engagement was significantly higher in the LIG and HIG post-intervention, particularly in the months following the initial notification. While no significant differences were found in antimicrobial prescription choice, a potential shift from 3rd-generation cephalosporins to clavulanic acid-potentiated amoxicillin was observed in the HIG feline group. No significant changes were observed in anti-inflammatory prescription frequency or euthanasia rates. Diagnostic test frequencies remained largely unchanged.

The findings strongly support the efficacy of social norm messaging and educational interventions in reducing HPCIA prescriptions in companion animal practice. The significant reductions observed in both the HIG and LIG, particularly in the feline population, highlight the potential of these approaches. The greater impact of the HIG underscores the benefit of providing more intensive support and feedback. The study's success in reducing overall antimicrobial use beyond HPCIAs suggests a broader positive shift in prescribing behavior. The increased portal engagement after notification shows the effectiveness of highlighting above-average prescribing rates as a motivator for change. The observed shift towards clavulanic acid-potentiated amoxicillin in felines requires further investigation to assess its impact on resistance development. The lack of change in diagnostic testing rates highlights an ongoing challenge in the field.

This RCT provides robust evidence supporting the effectiveness of a data-driven, multi-faceted antimicrobial stewardship program to reduce HPCIA and overall antimicrobial prescriptions in companion animals. Both light and heavy interventions proved effective, with the more intensive intervention yielding larger effects. Future research should focus on strategies to enhance diagnostic test utilization and optimize antimicrobial selection to minimize resistance development. The study's findings are being used to inform the development of a national antimicrobial stewardship scheme.

The study was conducted within a single large veterinary practice group, potentially limiting the generalizability of the findings to other practices with different management structures and cultures. The eight-month follow-up period may not be sufficient to assess long-term sustainability of the observed changes. The lack of granular data on individual staff interactions with the benchmarking portal hinders a precise understanding of the intervention's mechanism of action. The assessment of animal welfare outcomes was limited to euthanasia rates, potentially overlooking other subtle negative effects. The study primarily focused on HPCIA prescriptions, potentially overlooking the broader impact of non-HPCIA antimicrobial use.