Diarrhea is a common symptom in the horse that can be caused by a number of different factors. Inflammation of the large bowel, called colitis, is a common but serious disease of horses that results in diarrhea, fever, depression, and/or colic. There are many causes of acute colitis in horses which includes:

• Clostridiosis
• Potomac Horse Fever
• Phenylbutazone toxicity
• Blister Beetle Poisoning
• Plant Poisonings (less common)
• Chemical Poisonings (less common)
• Frequently the inflammation occurs with no known cause.

If you have diarrhea but do not know the cause you should start with the article Diarrhea in Horses, an Overview. This article will help you decide what type diarrhea you have and provide links to the appropriate article. This article concerns itself with the diagnosis, treatment, and prognosis of salmonella colitis. Recent scientific reports are included.

Clinical signs of colitis are those caused by infection, toxins, shock, colic, and diarrhea. Very early in the disease the horse may appear to be suffering from colic, but the heart rate will be a little higher, mid 50's to lower 60's, than the pain alone would account for. The horse will also have a low to moderate grade fever, not a typical sign of a medical colic. The gums may appear quiet pale. Usually a cow patty diarrhea will be present, which later will develop into a watery stool. I have seen some peracute colitis where the horse was down before diarrhea developed.

Banamine can temporarily improve these individuals early in the disease to the point that their appetite will return. In several hours however they will rapidly deteriorate. As shock develops the horses become depressed, weak and rapidly begin to show clinical signs of dehydration. Recumbency and death follow. The course of the disease can be from less than a day to a week or more depending on the severity of the inflammation, immune status of the individual, and treatment.

Remember, if you see colic associated with fever or diarrhea the time to act is now, fluid loss and toxemia can be so remarkable that just an hour or two may make a big difference.