Background: Antimicrobials essential for human health must be used judiciously. Objectives: Quantify current use and indications for critically important antibiotics (“protected antibiotics”) in general equine practice. Study Design: Prospective descriptive. Methods: Systemic use of 3 rd generation cephalosporins (ceftiofur), fluroquinolones (enrofloxacin and marbofloxacin), macrolides (clarithromycin), ansamycins (rifampin) and polymyxins (polymyxin B) (classified as “protected antibiotics”) were prospectively recorded in 19 equine practices over a six-month period (April - September 2023). Results: Protected antibiotics were prescribed to 200 horses with 10 horses prescribed two protected antibiotics concurrently. These included ceftiofur (48.2%), enrofloxacin (34.3%%), marbofloxacin (7.1%), polymyxin B (6.2%), rifampin (2.8%) and clarithromycin (1.4%). The mean number of protected antibiotics prescribed per practice was 10.5 (SD 12.4, range 0-41). The commonest clinical indications were respiratory disease (18.0%), foal septic diseases (16.5%), gastrointestinal diseases (15.0%), complicated wounds (13.5%), “dummy”/premature foals (7.5%) and cellulitis/lymphangitis (6.5%). Of 190 horses prescribed protected antibiotics, 76 (40.0%) were foals (less than 12 months of age). Horse age (foal or adult) was associated with specific antibiotic use (p < 0.001), with 73.7% of ceftiofur prescriptions for foals, and 97.0% and 100% of enrofloxacin and marbofloxacin prescriptions respectively for adults. Horses less than one year of age were less likely to have culture and antibiotic susceptibility testing (AST) compared to adults (P < 0.001). Commonest justifications for protected antibiotic use were lack of alternative preparations suitable for foals (27.5%), AST results (24.9%) and failure to respond to previous antibiotic treatment (17.1%). Main Limitations: Convenience sampling with small number of cases. Aminoglycoside use not evaluated. Conclusions: Respiratory and gastrointestinal diseases, complicated wounds and foal infections were the commonest reasons for protected antibiotic use. Lack of alternative drugs (for foals) and C&S results or failed previous treatments were commonest justifications.

Background: Monitoring antibiotic use (AMU) is a key component of antimicrobial stewardship. Published AMU data in equine hospitals are limited. Objectives: Document AMU in equine hospitals. Study Design: Repeated point prevalence surveys. Methods: Prospective descriptive study. AMU recorded one day weeky for 12 months in 6 equine hospitals. Results: 1142 horses were prescribed antibiotics among 15031 horses (7.6%) hospitalised on 216 survey days. Commonest breeds were Thoroughbreds/crosses (34.7%) and warmbloods/crosses (22.5%). Median age of adults was 6 years (IQR 10, range 1-28 years) and 8 weeks for foals (IQR 14 weeks, range 1 day-50 weeks). Mean weight of 1127 horses 420kg (range 15-866kg). Commonest indications were complicated wounds (23.6%), gastrointestinal/abdominal disease (19.2%), surgical prophylaxis (15.0%) and simple wounds (11.8%); 81.4% were community-acquired conditions, 14.4% surgical prophylaxis, 3.6% healthcare-acquired. Culture and susceptability performed in 11.4%. The commonest antibiotics prescribed were procaine penicillin (41.8%), gentamicin (41.4%), potentiated sulfonamides (16.5%), oxytetracycline (10.2%), ceftiofur (9.2%) and doxycycline (8.2%). Enrofloxacin prescribed in 59 horses (5.2%) and marbofloxacin in 19 (1.7%). The mean antibiotic dosages (mg/kg) ( + SD) were: procaine penicillin 20.5 ( + 2.8), gentamicin 7.1 ( + 1.0), potentiated sulfonamides 30.4 ( + 3.0), oxytetracycline 5.9 ( + 1.0), ceftiofur 5.2 ( + 1.4), doxycycline 5.9 ( + 1.7), enrofloxacin 6.6 ( + 1.1) and marbofloxacin 3.7 ( + 1.4). Main Limitations: Systemic AMU only. The duration of antimicrobial courses not recorded. Some cases may have been double (or more)-counted if they were in the hospital on >1 survey days. Conclusions: Antimicrobials were prescribed in 7.6% of hospitalised horses. Commonest indications were complicated wounds, gastrointestinal/abdominal disease, surgical prophylaxis and simple wounds. Commonest antibiotics administered were procaine penicillin, gentamicin, potentiated sulfonamides, oxytetracycline, ceftiofur and doxycycline. Critically important antimicrobial use was uncommon. Dose rates were generally appropriate.