Staying On Guard Against Equine Colitis

A brown breed horse looks quietly through a wooden fence on a green farm

Horses have delicate and complex gastrointestinal systems compared to many other animals, leaving them susceptible to digestive disorders, such as colitis. 

“The term ‘colitis’ means inflammation of the large intestine, which is most often accompanied by diarrhea,” explained Dr. Amanda Trimble, a clinical assistant professor of equine internal medicine at the Texas A&M School of Veterinary Medicine & Biomedical Sciences. “There are many different causes of colitis in horses, some potentially more severe than others, and associated signs largely depend on if the disorder is acute (rapid onset) or chronic (long-lasting).”

Because timely recognition and intervention are crucial to preventing the progression of colitis and minimizing its impact on a horse’s health, Trimble advises owners to closely monitor their horses for any signs so that if it arises, a veterinarian can determine the cause as soon as possible.

Recognizing Symptoms

When the delicate balance of a horse’s digestive system is disrupted, the large intestine can become inflamed and not absorb water as it should, causing the typical watery and frequent bowel movements associated with colitis. The excessive loss of fluids through persistent diarrhea can make horses extremely dehydrated and, if left untreated, can lead to additional symptoms, depending on whether the condition is acute or chronic.

Acute colitis can be life-threatening because of the rapid dehydration that can result from the diarrhea’s sudden and potentially severe nature. Symptoms of acute colitis that can accompany diarrhea include:

  • Lethargy
  • Colic, or abdominal pain
  • Lack of appetite
  • Fever greater than 102 degrees Fahrenheit
  • Tacky mucous membranes, as evident by dry gums or dry lower eyelids
  • Signs of endotoxemia, a bacteria from the gut that circulates around the body; these include toxic lines on the gums, which look like a dark red-purple line just above the front incisor teeth; tachycardia, or a heart rate at 60 beats per minute; injected sclera, or the reddening of white parts of the eye; and laminitis

Chronic colitis, on the other hand, is a condition that usually develops over time and can cause a loss of essential nutrients in addition to a loss of fluids.

“Because horses are losing protein through their gut, some signs you may see for more chronic cases – commonly caused by parasites, sand ingestion, or inflammatory bowel disease – are weight loss and edema, a type of swelling in the legs or lowest part of the abdomen,” Trimble said.

Equine Colitis Culprits

It is important for owners to contact a veterinarian as soon as they notice the development of diarrhea or other symptoms so that the veterinarian can determine the underlying cause.

“There are infectious causes of equine colitis that can spread from horse to horse – or even horse to human – through feces, including potomac horse fever, salmonella, equine coronavirus, and clostridial diseases,” Trimble explained. “Small strongyles (a type of intestinal parasite), an altered gut microbiome from diet changes, sand ingestion, or antibiotic use may cause colitis as well.”

Although it is rare, Trimble pointed out that noninfectious colitis can also be a symptom of tumors, inflammatory bowel disease, or the overuse of certain nonsteroidal anti-inflammatory drugs meant to relieve pain and reduce inflammation.

In some horses, diarrhea can be confused with fecal water syndrome, a condition that looks similar to colitis.

“We are unsure the cause of fecal water syndrome, but it is characterized by increased water coming before or after the feces in otherwise healthy animals,” Trimble said. “Other than being frustrating for the owners to manage, it is not a serious threat to horses; however, we still recommend contacting your veterinarian if you notice the signs.”

Different causes of colitis may require different treatment approaches, so owners should work with their veterinarian to ensure timely care.

“Providing care early is critical, as horses can become seriously dehydrated very quickly,” Trimble explained. “Owners should give their veterinarian a good history of any management, environment, herd, or medication changes to help them determine how to best treat the horse.”

By staying vigilant about digestive changes in your horse and collaborating with veterinarians, horse owners can play a vital role in the well-being and quick recovery of their equine companions.

Pet Talk is a service of the School of Veterinary Medicine & Biomedical Sciences, Texas A&M University. Stories can be viewed on the web at Suggestions for future topics may be directed to

Show Buttons
Hide Buttons