Pharmacoepidemiology
Characterizing the Epidemiology of Antimicrobial Use in a Large U.S. Municipal Companion Animal Shelter Paulina Colombo* Paulina Colombo Colombo Colombo Colombo Colombo Colombo Department of Epidemiology and Biostatistics, Mel and Enid Zuckerman College of Public Health, University of Arizona, Tucson, AZ 85724, USA
Background: Responsible antimicrobial use (AMU) in animals is essential to optimize care and minimize antimicrobial resistance (AMR). While AMU guidelines exist in animal production and small animal clinics, gaps remain for animal shelters. The University of Minnesota (UMN) and World Health Organization (WHO) have proposed AMR frameworks to classify animal antibiotics by AMR and public health risk. This study aimed to (1) characterize AMU in a large, municipal shelter; (2) calculate species-specific days of therapy (DOT); and (3) determine differences in prescribing of high-risk antibiotics by species. Method: Electronic records (Jan 2022–Jun 2025) were analyzed to calculate AMU per 1,000 shelter-days for dogs and cats. Prescriptions were categorized by UMN clinical tiers and by public health importance per the 2024 WHO framework. GEE models accounting for non-independence of prescribing events by animal were used to model prescription of “Second-line” (UMN) and “Critically Important” (WHO) AMU by species. Result: Over 3.5-years, 26,509 antibiotic prescribing events occurred for 15,784 unique animals. 30% of cats and 34% of dogs received antibiotics. Cats had shorter average courses than dogs (4.8 vs 6.1 days). Penicillins, tetracyclines, and cephalosporins were the most frequently prescribed classes. AMU was 249.5 DOT/1,000 shelter-days for cats and 173.0 for dogs. Under UMN tiers, 29.3% of canine and 10.9% of feline prescriptions were “Second-line” therapies (culture/sensitivity needed). Under the WHO framework, 29.3% of canine and 10.6% of feline prescriptions were “Critically Important” antimicrobials. Dogs had higher odds of receiving “Second-line” (OR 3.70; 95% CI: 3.37-4.07) and “Critically Important” (OR 3.90; 95% CI: 3.52-4.29) antibiotics (p<0.001). Conclusion: Compared to dogs, cats had 44% higher overall antibiotic DOT/1000 shelter-days. In contrast, dogs had over 3 times the rate of WHO “Critically Important” prescriptions (to humans) compared to cats.