Horseman’s Forum, 2014
The Trots (not the pretty kind): Review of Equine Diarrhea, by Dr. Sandy Taylor
As a horse owner, it is important to recognize when your 4-legged friend’s fecal consistency changes. Very dry manure
can cause impaction colic, while diarrhea can cause severe dehydration and subsequent organ failure. Recognition of
what is normal for your horse is key, so that you will quickly recognize a problem. The majority of horses with highvolume diarrhea have colitis (inflammation of the large colon). There are several causes of colitis, which can be divided
into infectious and non-infectious categories. Infections are usually caused by bacteria, and include Neorickettsia risticii
(Potomac horse fever), Clostridium difficile, Clostridium perfringens, Salmonella sp., Lawsonia intracellularis and
Rhodococcus equi. Non-infectious causes of colitis include sand irritation/impaction and toxins (e.g. cantharadin from
Blister Beetles, non-steroidal anti-inflammatory drug toxicity, oleander, etc.). Intestinal cancer and inflammatory bowel
disease can cause diarrhea from decreased absorption of water in the colon, but do not typically cause colitis. Similarly,
enteroliths (intestinal stones) can cause diarrhea in addition to chronic colic, but inflammation of the colon is not usually
seen. Diagnostic tests to determine the cause of diarrhea typically include routine blood work (complete blood count,
biochemical analysis, blood gas), abdominal ultrasound to image the intestines, and testing of manure for bacterial
infection. Abdominal x-rays may be required if sand impaction or enteroliths are suspected, and analysis of abdominal
fluid that surrounds the intestines can help determine the degree of intestinal inflammation. Regardless of the cause of
diarrhea, treatment consists of replacing the horse’s fluid and protein deficit, and providing maintenance fluid therapy.
There are specific treatments for particular causes of diarrhea, and prevention strategies that may be implemented.
Complications of colitis include laminitis (founder; separation of the coffin bone from the hoof wall), vein clotting or
infection after IV catheter placement, chronic diarrhea, and weight loss. In summary, if your horse does develop a
change in fecal consistency, call your veterinarian immediately! If your horse needs to be hospitalized for diagnostic
testing and treatment, he/she will be housed in our isolation facility in case a contagious disease that can be spread to
other horses is identified. Our health care team, including students, residents, technicians and faculty, will all be
involved in the care of your horse and are dedicated to achieving the best possible outcome.