Scientists Test Probiotic for Interrupting C. Difficile Outbreaks in Foals
Foals lack the established populations of beneficial bacteria in their gastrointestinal (GI) tracts that adult horses have. This makes way for bacteria such as Clostridium difficile to set up shop instead, causing a variety of GI signs and even death. During a recent C. difficile neonate outbreak at a Thoroughbred farm, researchers sought to find out if a probiotic could make a difference.

Steven Frese, PhD, a microbial ecologist with Evolve Biosystems, which funded the study led by Monica Aleman, MVZ, PhD, Dipl. ACVIM, and John Madigan, DVM, MS, Dipl. ACVIM, of the University of California, Davis, described C. difficile infection and the research findings at the 2017 American Association of Equine Practitioners’ Convention, held Nov. 17-21 in San Antonio, Texas.

Shortly after birth, foals might develop C. difficile-associated disease, causing enterocolitis (inflammation of the small intestine and colon), diarrhea with or without blood, fever, reduced feed intake, and lethargy. The standard course of treatment—administering an antibiotic such as metronidazole—is not always effective, due to drug resistance, and so C. difficile can be a cause of mortality on breeding farms.

Mare’s milk contains short chains of simple sugars known as oligosaccharides that get broken down by bacteria in the foal’s GI tract. The end product differs, depending on whether pathogenic (disease-causing) or beneficial bacteria do the breaking down.

It is possible that probiotics containing beneficial bacterial strains could alter fermentation end products to benefit foal health, said Frese.

In this study, the researchers evaluated 41 Thoroughbred foals over one foaling season at a private breeding facility where veterinarians had detected C. difficile previously. Prior to the study many foals there had developed C. difficile-related diarrhea, three of which died—in fact, the outbreak was ongoing.

The researchers dosed 28 foals with a probiotic mixture (Bifidobacterium longum infantis and Lactobacillus plantarum, strains of beneficial bacteria known to consume milk oligosaccharides) twice a day for their first two days of life and cared for the rest normally without the probiotic. They reported no cases of C. difficile-associated diarrhea in the treated foals, whereas untreated foals continued to get sick.

Also, fewer foals receiving the supplement developed foal-heat diarrhea (which often occurs when the dam goes back into heat) during the 14-day study, said Frese.

Upon analyzing fecal samples, the team noted significantly higher numbers of Bifidobacterium in the feces of foals receiving the probiotic than in feces of untreated foals, suggesting the probiotic had successfully altered the GI microbiota’s composition, said Frese. This effect persisted for the length of the study and 12 days after the last supplementation.

This research suggests that using a targeted probiotic might be an effective way to reduce C. difficile-associated diarrhea in neonatal foals, he said.