Colitis-X in Horses

By PetMD Editorial on Nov. 2, 2011

Colitis-X is a serious intestinal condition that is not very well understood. Often fatal, its cause is unknown although it appears to affect horses under stress such as stress caused by transport or surgery. This is often a catch-all term used when a more definitive diagnosis for the cause of the diarrhea has not been found.

This condition progresses extremely fast, with severe watery diarrhea being the most obvious clinical sign. The fluid loss from the diarrhea is so severe that dehydration quickly sets in, causing hypovolemic shock and death. Emergency treatment may be attempted, but it is rarely successful. The death rate for this condition approaches 100%.

Symptoms and Types

  • Severe depression
  • Recumbency
  • Dark red to purple mucous membranes (gums)
  • Rapid heartbeat
  • High temperature/fever followed shortly by abnormally low temperature
  • Severe watery diarrhea
  • Mucous in stool
  • Dehydration
  • Pain in abdomen
  • Hypovolemic shock
  • Death (usually follows shock from sudden drop in temperature and loss of body fluids)


  • Specific cause is currently unknown
  • Linked to high stress such as transport or extensive surgery
  • Some cases have been reported to follow treatment with the antibiotics tetracycline and lincomycin.
  • May also be linked to peracute Salmonella or Clostridial bacterial infections


Colitis-X is a diagnosis of exclusion, meaning it is used when no other cause for the severe diarrhea can be found. Given the rapid progression of this disease, it is extremely challenging to institute treatment and determine a diagnosis before the death of the horse.

Necropsy (animal autopsy) can sometimes aid in the diagnosis of this condition, as all cases show similar damage to the lining of the intestines.


Because of the rapid decline in health that results from this intestinal disease process, colitis-X is known for its exceptionally high rate of mortality; 90-100 percent of horses affected by this condition will die. It is important to keep in mind that most treatments for colitis-X are unsuccessful. In most instances, the disease has progressed too far for treatment.

For those cases in which treatment can be started immediately and at a properly prepared clinical facility, therapy consists of large amounts of fluids and electrolyte replacement given to counteract the fatal effects of the rapid dehydration. This initial treatment typically needs to be followed immediately by blood plasma infusions to replace the loss of body fluids, along with intestinal support – such as the administration probiotics to encourage the growth of "good" bacteria.

Corticosteroids (anti-inflammatory steroids) in high doses may also be used to combat the shock the horse goes into following the initial increase in body temperature and subsequent severe drop in body temperature. To resist the effects of toxins being released into the body, an anti-inflammatory non-steroidal drug, flunixin meglamine, may be used to prevent toxemia, as well as for palliative treatment -- to reduce inflammation in the intestinal tract, relieving the horse of some of the immediate discomfort.


As the cause of this condition is still unknown, there is currently no vaccine available to prevent colitis-X nor are there effective ways to prevent it. The best practical prevention includes ensuring your horse is in excellent health when being transported or undergoing other forms of stress such as competition. Proper hygiene is also important. It is also important to be especially vigilant of any sudden change in health when your horse is on a course of antibiotics, and after a major surgery.

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