Rethinking How We Fight Infection in Horses

Here are questions veterinarians should consider when deciding whether to treat a horse with an antibiotic.

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Antibiotic overuse in horses can lead to drug resistant bacteria strains. | Adam Spradling/The Horse Staff
The rise of “super bugs”—bacteria resistant to multiple antibiotics—has become a global health threat, one that’s making equine veterinarians rethink their strategies for treating infections.  

At the 2021 American Association of Equine Practitioners Convention, held Dec. 4-8 in Nashville, Tennessee, Emily Feyes, DVM, MPH, Dipl. ACVPM, outlined the multipronged approach veterinarians at The Ohio State University Veterinary Medical Center (VMC) are using to combat this problem. Feyes is the previous director of the VMC’s new Antimicrobial Stewardship Program (ASP), which is being shared with veterinarians in the state through a partnership program, the Buckeye ASP. Antimicrobial stewardship builds on the basics of good care, effective vaccines, infection control and prevention, and biosecurity measures that safeguard people, animals, and the environment.  

Feyes explained that antimicrobial stewardship is about using “the right drug at the right dose for the right duration” to maximize success, minimize adverse effects, and reduce the risk of bacteria developing resistance. Sometimes it means not using an antibiotic at all, and instead opting for other measures to manage illness or injury. 

The VMC modeled its antimicrobial stewardship program on those developed in human medicine. Prescription drug monitoring, environmental surveillance, and education are key components. The idea is not to police veterinarians, Feyes said, but rather to review prescribing practices, promote effective hygiene strategies, and share better data. 

Antibiotic use is driving antimicrobial resistance—even when these drugs are prescribed appropriately. Feyes said an ongoing challenge for many practitioners is a lack of rapid (and economical) diagnostic testing. She suggested the use of “antibiograms” as an alternative to better target pathogens (disease-causing organisms) when individual test results are unavailable. Essentially, an antibiogram is a summary of antimicrobial drug susceptibility data from organisms isolated within certain patient populations, which veterinarians can use to guide therapy. Veterinarians can use antibiograms from their own practices or their geographic region.  

Veterinarians are often reluctant to delay starting antibiotics while awaiting their patients’ lab results; they want to give the horse every chance for prompt improvement. They might also feel pressure from anxious owners. Nevertheless, Feyes suggests practitioners consider the following questions as they weigh treatment options:  

  • What type of infection is it? 
  • Where is the infection located? 
  • What are the typical organisms cultured from this region of the body? 
  • Does it require an antibiotic, or could it resolve with supportive therapy? 
  • Does it have to be a broad-spectrum antibiotic, or could it be a narrow-spectrum drug? 
  • Does it have to be given systemically, or could treatment be localized? 

The thought here is to encourage critical thinking rather than reflexively doing what the practitioner (and likely his or her peers) has always done. Feyes also borrowed a phrase from human medicine known as an “antibiotic timeout,” which means reevaluating the patient 48 hours after beginning treatment. Is the animal better, the same, or worse? Have the lab results come back, and do those results support the original treatment plan? 

Feyes also recommended putting infection control plans in place that include protocols for cleaning and disinfecting, isolating and moving animals, and surveillance to monitor the protocols’ efficacy to ensure the safety of people and animals alike. 

Antibiotics revolutionized medicine. Today, the imperative is to preserve the efficacy of these drugs so they remain potent allies against infection far into the future. It’s reason enough to put an antimicrobial stewardship program in place, and The Ohio State’s VMC is leading the way. 


Written by:

Betsy Lynch has been an equine industry professional for 30-plus years as an editor, writer, photographer, and publishing consultant. Her work appears in breed, performance, and scientific journals. Betsy owns her own business, Third Generation Communications. She is a graduate of Colorado State University, continues to keep horses, and lives near Fort Collins, Colorado.

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