Antibiotics prescribing patterns and association with system-specific pathologies in equine veterinary practice: Insights from a 12-year study at a veterinary teaching hospital.

Abstract: Antibiotics are essential in veterinary medicine, enhancing animal health and welfare. However, widespread use contributes to resistance, increasing the risk of treatment failure and the transmission to humans. Objective: Analyze antibiotic prescribing practices in an equine internal medicine unit, focusing on factors influencing use, particularly Highest Priority Critically Important Antimicrobials (HPCIAs). Methods: 1315 adult equids, including horses, donkeys and mules, presented for different diseases to the Veterinary Teaching Hospital (VTH) of the University of Pisa from 2011 to 2023. Retrospective study focused on the prudent antibiotics use in equids. Medical records were reviewed, and data were extracted from the VTH management system, including antimicrobial class, patient characteristics, and body system/system-specific pathology. Results: Antibiotic use varied significantly across system-specific pathology (p < 0.001), with highest usage in integumentary, ocular, and respiratory conditions. Aminoglycosides were the most frequently administered class, followed by tetracyclines and fixed-dose combinations (preparations containing two or more antimicrobial active ingredients). Over time, antibiotic class usage shifted significantly (p < 0.001). Ceftiofur and gentamicin were used in pneumonia and pleuropneumonia, oxytetracycline was mainly used for piroplasmosis, and tobramycin for corneal ulcers. Combination therapy, particularly gentamicin-ceftiofur, was most commonly used for respiratory infections. Conclusions: Antibiotic prescribing patterns in equine practice are heterogeneous and directly linked to system-specific pathologies. The observed use of HPCIAs, coupled with the dominance of aminoglycosides and tetracyclines, highlights areas where prescribing practices could be optimized. These results suggest the relevance of developing and implementing targeted Antimicrobial Stewardship (AMS) strategies, focusing on evidence-based diagnostics and educational programs.