Diarrhea is among the most common clinical complaints in foals. According to a National Animal Health Monitoring System equine study in 1998, diarrhea affected more than 20% of foals within the first six months of life. Although diarrhea is common with enteritis (inflammation of the small intestine), diarrhea is not always associated with inflammation of the bowel. Before the veterinarian can consider a treatment course for diarrhea, he must understand the mechanisms of diarrhea. Is it malabsorptive or secretory diarrhea? Malabsorptive is the inability of the intestinal tract to reabsorb water and nutrients. Secretory diarrhea results in the hypersecretion of both water and electrolytes into the intestinal tract. In a general categorization, bacterial toxins (salmonella or clostridium spp, for example) cause a secretory diarrhea while viruses such as rotavirus and coronavirus can result in a malabsorptive diarrhea. In severe infections, bacteria and viruses can result in both secretory and malabsorptive diarrhea. Diagnosing the cause of diarrhea in foals can be difficult because of the myriad potential causes. Causes of foal diarrhea may be secondary to non-infectious foal heat diarrhea and dietary issues, bacterial infection (salmonella, clostridium difficle, and perfringens), viral infection, parasitic infection, and cryptosporidium. Obtaining fecal samples for either culture(s) or PCR (DNA) testing can be utilized in identification of a specific agents. Unfortunately, despite significant advances in veterinary diagnostic technology, the diagnostic rate for fecal testing is almost identical to that in human medicine—or about 50% to 60%. While there is no “golden bullet” to treat foal diarrhea, treatment strategies are directed at both supportive care (fluid therapy, nutrition) and treatment for specific infections as directed by clinical and diagnostic testing. One novel treatment plan currently used as an adjunctive treatment for both viral and bacterial causes of diarrhea is the use of Bentonite clay. Bentonite is effective because it bonds to a variety of toxins and prevents the absorption of toxins by coating the intestinal wall. Not all bentonite clay is created equally, but there is an ultra-purified bentonite clay that is available for use in equine patients.

This question has been answered by Nathan Slovis, DVM, the director of the McGee Medical and Critical Care Center at the Hagyard Equine Medical Institute in Lexington. He is a native of Annapolis, Maryland. Slovis received his Bachelor of Science from Radford University, Doctor of Veterinary Medicine from Purdue University, interned at Arizona Equine Center, and completed his residency in internal medicine at the University of California-Davis. Slovis has published articles in the Journal of the American Veterinary Medical Association, Journal of Veterinary Internal Medicine, Equine Veterinary Journal,and Clinical Techniques in Equine Practice. He also implemented the current Infectious Disease and Equine Emergency Response Programs at Hagyard Equine Medical Institute and holds the position of Infectious Disease Officer and Equine Emergency Response Director.