Infectious Diseases

Study Finds ABX Overtreatment Common in Hospitalized Foals

By Adam Marcus

If practice in Canada is a guide, foals hospitalized in the ICU with infections are overtreated routinely with the broad-spectrum antibiotic ceftiofur when other drugs would be equally effective and less likely to promote drug-resistant infections, researchers have found.

The study used data from the veterinary records of 60 neonates (age range, 0 to 30 days; 1 week of age or younger, 70%) treated with antibiotics at the University of Montreal’s equine ICU in 2023. The researchers analyzed data about the choice of antibiotic, septic scores and other patient characteristics.

Records showed that 80% of the foals received a first-line antibiotic at some point during their care. Ceftiofur—a third-generation cephalosporin that the WHO considers a “critically important” agent for humans—was the choice in 63% of cases, according to the researchers. About half (52.5%) of these animals went on to receive penicillin plus gentamicin.

Results of antimicrobial susceptibility testing (AST) led to a change of antibiotic in 14 cases (23%)—underscoring the importance of taking samples for bacteriological culture “as often as possible,” said Daniel Jean, DVM, PhD, DACVIM-LA, a professor of equine internal medicine at the University of Montreal, who presented the findings at the 2025 ACVIM Forum, in Louisville, Ky.

Overall, 50 foals (83%) survived to hospital discharge. However, the researchers found no link between the odds of survival and the types of antibiotics received during treatment. Nor did the extent of sepsis on admission appear to affect rates of mortality, which Dr. Jean said came as a surprise.

“This study highlights the frequent use of highest-priority critically important antimicrobials in pediatric patients at an equine teaching hospital. The AST results allowed for targeting antibiotic therapy in nearly one-quarter of pediatric patients,” Dr. Jean and his colleagues reported.

The misuse of ceftiofur generally has been described before. As the authors of a 2023 review in the Equine Veterinary Journal wrote, equine veterinarians have long strayed from antibiotic guidance issued by professional societies in the United States, Canada and Europe.

Studies have found misuse of antimicrobials for the treatment of equine asthma, viral respiratory infections and other conditions, they wrote. Globally, veterinarians show poor adherence to recommendations against using later-generation cephalosporins as first-line agents, and a lack of adherence to proper dosing, including making errors in weight-based calculations and timely administration of the drugs. Antimicrobial susceptibility testing is also widely underused, the authors of the review wrote.

“Observations provided by these studies clearly demonstrate that the current state of antimicrobial stewardship amongst veterinary students and equine practitioners is inadequate,” the researchers wrote. “Antibiotic stewardship can improve only if practitioners are familiar with characteristics of the antibiotics available to them.”

Dr. Jean acknowledged that while the findings indicate significant room for improvement in antibiotic stewardship in pediatric patients, making the optimal decision in real-time can be challenging for clinicians.

“The decision is not easy, because there is a trend for clinicians to choose to use ceftiofur in the first intention, even though this antibiotic is a first-class category drug in Canada,” Dr. Jean told Modern Equine Vet. “But this study highlights the fact that the survival rate is quite similar, whatever the antibiotic used in foals. So, I think for most of these cases, the combination of penicillin plus gentamicin should be the first choice, except if the patient has renal dysfunction or if the antimicrobial susceptibility test justifies not using” the combination.

Dr. Jean said his impression is that equine veterinarians are more willing to start with ceftiofur in foals than in adult horses, “but this is a perception” for which he lacks data. MeV