Equine inflammatory bowel disease (IBD) is a term used to describe a chronic malabsorptive and maldigestive disorder affecting the horse's gastrointestinal tract. In adult horses, equine IBD is defined as an infiltration of the mucosa and submucosa with abnormal cells. In foals, IBD is most frequently associated with malabsorption caused by infectious agents. Equine IBD is further broke down into specific diseases, which include:

• Equine eosinophilic gastroenteritis (EEG): EEG is a diffuse inflammatory cell infiltration of the small intestinal mucosa with eosinophils and lymphocytes. The more severe form of the disease is referred to as multisystemic eosinophilic epitheliotrophic disease (MEED). EEG can affect horses of any age, sex, or breed, but occurs most commonly in young (between 2 to 4 years of age) Thoroughbreds and Standardbreds. The most frequent clinical sign observed in horses with EEG is recurrent colic. Horses with MEED may have severe dermatitis that resembles pemphigus foliaceus with lesions observed on the face, ventrum, coronary bands, and limbs.
• Equine granulomatous enteritis (EGE):EGE has many parallels to Crohn's disease in humans and Johne's disease in cattle. It is characterized by lymphoid and macrophage infiltration of the mucosal lamina propria, with several types of plasma and giant cells. The ileum is generally the most severely affected part of the gastrointestinal tract. The exact cause of EGE is unknown, however exposure to aluminum through invading microorganisms, particularly parasites, has been directly linked to EGE in horses. Horses of any age, sex, or breed can develop EGE, however young (between 1 and 5 years of age) Standardbred horses appear to be more susceptible to developing EGE.
• Lympho-plasmacytic enteritis (LPE): LPE has been thought to be an early stage of intestinal lymphosarcoma. It is characterized by excessive infiltration of lympho-cytes and plasma cells in the lamina propria of the gastrointestinal tract with the absence of granulomatous change. Horses of any age, breed, or sex can develop LPE. Usually horses with LPE do not present with clinical signs until the advanced stages of the disease, and thus is usually associated with a poor prognosis for affected horses.

Horses with equine IBD present with varying clinical manifestations. The most commonly reported clinical signs include colic, weight loss, and/or diarrhea. Signs can occur recurrently, intermittently or even seasonally.

Equine IBD can be difficult to diagnose, and requires multiple tests, equipment and examinations to do so. The clinical signs of equine IBD are similar to several other equine diseases and conditions, which need to be ruled out.