Beyond being a pain in the gut, equine gastrointestinal (GI) diseases are expensive to deal with. Take a diarrhea outbreak, for instance: Diagnosing the cause, implementing biosecurity measures, eliminating the infectious agent, and returning to business-as-usual involves significant amounts of time and money.

Nathan Slovis, DVM, Dipl. ACVIM, is infectious disease specialist and equine emergency response director at Hagyard Equine Medical Institute, among other roles at the Lexington, Kentucky, and he’s researched a variety of equine GI diseases and how they spread on farms and in clinics. In a sunrise session at the 2015 American Association of Equine Practitioner’s convention, held Dec. 5-9, in Las Vegas, he and Ron Vin, DVM, Dipl. ACVIM, of Myhre Equine Clinic, and Christian Leutenegger, DrVetMed, PhD, FVH, of IDEXX Veterinary Laboratories, described emerging equine GI diseases, how to detect them, and how to avoid them in the first place.

Foal Diarrhea

The presenters said that GI disease can be difficult to manage, particularly in foals. The National Animal Health Monitoring System reported in its 1998 study that 20% of foals develop infectious diarrhea by six months of age. In a more recent study¹, published in 2009, researchers found an infectious agent in 55% of foals with diarrhea, but this begs the question: Does that infectious agent cause the diarrhea?

Identifying which pathogens are involved in a horse’s GI illness is essential determining the cause of disease. Veterinarians can perform a rapid diagnostic test on fecal samples using a PCR (polymerase chain reaction) test—the chain reaction makes millions of copies of a pathogen’s DNA to enable analysis. Slovis said that the load of virus in the sample is the best indicator of disease outcome, both in terms of degree of illness and the speed of resolution. PCR is also useful for identifying genes from bacteria that produce toxins