Researchers Examine Link between Salmonella and Colic

One of the most critical elements of operation for a major equine hospital is biosecurity, which can be challenging for facilities treating critically ill patients. Horses recovering from acute colic or colic surgery are among the most medically vulnerable to secondary illness, due in part to environmental and physical stressors, as well as potentially undergoing general anesthesia and a major abdominal surgery.

Researchers at the University of Pennsylvania's New Bolton Center recently completed a study examining the link between acute colic and Salmonella shedding. Horses with salmonellosis often have obvious signs of diarrhea, fever, and low white blood cell count (termed "leukopenia"). But researchers estimate that 1-2% of clinically normal horses shed the bacteria in their feces. This number likely rises when horses are stressed, as they would be following an acute medical or surgical colic episode.

While most large animal hospitals conduct fecal culture testing to identify potential Salmonella shedders, test results can take several days to return, which might not allow veterinarians to begin the necessary biosecurity protocols immediately.

To identify warning signs of horses shedding Salmonella, the research team--led by Barbara Dallap-Schaer, VMD, Dipl. ACVS, ACVECC--examined the medical records of 59 Salmonella-positive horses and 108 Salmonella-negative horses admitted to New Bolton Center. Only horses admitted for acute colic without diarrhea at presentation were included in the study.

The team found that Salmonella-positive horses not exhibiting signs of diarrhea at presentation tended to be patients whose colic was severe enough to warrant surgery, particularly if the colic stemmed from severe inflammation or vascular compromise in the gut rather than a simpler case of impaction. They also noted that Arabians and Warmbloods were at increased odds of shedding compared to Thoroughbreds. Horses more likely to shed also exhibited tachycardia (high heart rate) or gastrointestinal reflux during treatment and lethargy and inappetence for at least one day or more while in the hospital.

"These are important signs to know if you have a horse with colic, or you work in or manage a hospital that treats horses with colic," said Dallap-Schaer, an associate professor in the Department of Clinical Studies at New Bolton Center.

"The more rapidly one can identify horses likely to shed, the more effectively one can limit environmental contamination and the risk of subsequent transmission to other patients," she added. "From this study, it is probably safe to say that Salmonella shedding can be associated with more serious cases of colic."

Helen Aceto, PhD, VMD, director of biosecurity at New Bolton Center, explained that it's important to follow routine health and hygiene procedures when dealing with a colicking horse in the event the horse is a Salmonella shedder. The authors suggest those working at a large animal clinic focus fecal-testing efforts around horses matching risk factors for bacterial shedding and take the appropriate biosecurity precautions to prevent cross contamination to other patients.

The study, "Identification of predictors of salmonella shedding in adult horses presented for acute colic," appeared in the September/October 2012 issue of the Journal of Veterinary Internal Medicine. The abstract is available online.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.