A review of reported cases of inflammatory bowel diseases (IBDs) of horses for which no etiology was identified included cases of granulomatous enteritis (GE), multisystemic eosinophilic epitheliotropic disease (MEED), lymphocytic-plasmacytic enterocolitis (LPE), and idiopathic eosinophilic enterocolitis (EC). The terms EC and MEED were both used to describe a disease in horses characterized by infiltration of intestine and extraintestinal tissues with eosinophils. We use EC to describe IBD characterized by only intestinal infiltration by eosinophils. Horses with GE, MEED, or LPE are usually examined because of weight loss and depression, but horses with EC are usually examined because of signs of abdominal pain. Typically, horses with IBD have low concentrations of serumal proteins, especially albumin, and fail to adequately absorb glucose or xylose. Antemortem diagnosis of IBD can only be made by histologic examination of affected intestine. In some cases, antemortem diagnosis is made from histologic examination of rectal mucosa obtained by biopsy. Suspected causes of IBD in the horse include abnormal immune response to bacterial, viral, parasitic, or dietary antigens. Most horses with IBD do not survive, but horses with EC are more likely than those with LPE, MEED, or GE to respond to treatment. Successful treatments of horses with IBD include resection of grossly affected intestine and administration of corticosteroids.Key words: Eosinophilic enterocolitis; Granulomatous enteritis; Lymphocytic-plasmacytic enterocolitis; Multisystemic eosinophilic epitheliotropic disease.C hronic inflammatory bowel diseases (IBDs) are associated with dysfunction of the gastrointestinal tract due to infiltration of the mucosa and submucosa with populations of eosinophils, plasma cells, lymphocytes, basophils, or macrophages. 1,2 Clinical signs of IBD in the horse include weight loss, dependent edema, and lethargy and are usually associated with protein-losing enteropathy and malabsorption of nutrients, including glucose. Affected horses may have diarrhea or signs of abdominal pain. Signalment, clinical signs, clinicopathologic findings, and postmortem lesions may be highly characteristic of some types of IBD in the horse, but, in general, clinical and gross pathologic features of these diseases are similar, and a final morphologic diagnosis is based on histologic examination. When an etiologic diagnosis of IBD has been reported, mycobacterial 3-12 or parasitic infections, 13,14 or toxins 15 have been identified. The purpose of this report is to describe distinguishing features and discuss possible etiologies of the idiopathic IBDs and to discuss treatment of affected horses.
Granulomatous Enteritis (GE)This idiopathic condition was 1st reported in 1974 by Cimprich, 7 who noted the histologic similarity between this disease and Crohn's disease in humans. In our review of the reports of idiopathic GE, we found detailed descriptions of 47 affected horses. 6,7,9,[16][17][18][19][20][21][22][23][24][25] Of these, 32 were Standardbr...