Toxin Test Might Identify Horses with Diarrhea that Could be Debilitating

Early identification of a toxin produced by the diarrhea-causing bacterium Clostridium difficile, in the feces of horses with diarrhea might help identify which horses are at risk for developing serious disease, report researchers from the University of California, Davis, School of Veterinary Medicine.

Diarrhea in horses can range from a mild, self-limiting condition to a severe disease with life-threatening complications. One of the more dangerous causes of diarrhea in horses is the bacterium Clostridium difficile, which is known to produce at least two different toxins (A and B).

"Measuring toxin A levels in horses that present with diarrhea may play an important step in identifying horses at-risk for developing a more severe diarrhea."
--Dr. Gary Magdesian
"Early diagnosis of diarrhea due to C. difficile is an important step in minimizing morbidity and mortality associated with infection," explained K. Gary Magdesian, DVM, Dipl. ACVIM, ACVECC, ACVCP, an associate professor in the department of Medicine and Epidemiology.

To test a hypothesis that horses which tested positive for toxin A in their feces would have more severe disease than diarrheic horses negative for toxin A, Magdesian and colleagues tested the feces from 292 diarrheic horses and foals for C. difficile (the bacterium itself), C. difficile antigen, and C. difficile toxin A in fresh fecal samples.

"Our results showed that horses positive for the C. difficile toxin A in their feces had a higher band neutrophil count (a type of white blood cell commonly elevated in sick animals), a higher rectal temperature, and a higher mortality rate than horses negative for toxin A," explained Magdesian.

These results suggest that horses with measurable toxin A in their feces have a more severe clinical disease than diarrheic horses without measurable fecal toxin A levels.

According to Magdesian, "Measuring toxin A levels in horses that present with diarrhea may play an important step in identifying horses at-risk for developing a more severe diarrhea."

The study, "Comparison of clinical, microbiological, and clinicopathologic findings in horses positive and negative for Clostridium difficile infection," was published in the March 16 edition of the Journal of the American Veterinary Medical Association. Co-authors were Rebecca Ruby, MS, and Philip H. Kass, DMP, PhD, Dipl. ACVPM.

About the Author

Stacey Oke, DVM, MSc

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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