South African Equine Veterinary Association Congress 2015 Protea Hotel Stellenbosch
that more subtle forms of these diseases also occur in horses with mild weight loss or recurrent
colic. IBDs should be considered in horses with weight loss or recurrent colic in which other
problems (e.g., gastric ulcer disease, parasitism, sand accumulation, NSAID sensitivity, etc.) have
been excluded. Although both are non-specific findings, detection of mild to moderate
hypoalbuminemia and thickened intestinal walls on transabdominal ultrasonography can be
supportive findings. Additional diagnostic tests worthy of consideration include a carbohydrate
(CHO) absorption test (Figure 4) and bowel biopsies (multiple samples collected at surgery or a
rectal mucosal biopsy as a screening test) (Figure 5). IBDs are further characterized by
histological changes in the bowel mucosa and submucosa into distinct diseases.
Figure 4. Carbohydrate (glucose, 1 g/kg,
administered as a 20% solution by nasogastric tube
after an overnight fast) absorption test results
comparing expected results for normal horses,
horses with granulotamous enteritis (GE) and
horses
with
multisystemic,
eosinophilic,
epitheliotropic disease (MEED). This test is a
specific test for carbohydrate absorption in the
small intestine.
Granulomatous enteritis. Granulomatous enteritis (GE) is characterized by weight loss and soft
feces can accompany more advanced stages of the disease. Diagnosis is supported by “flat” CHO
absorption curves due to small intestinal involvement and evidence of lymphocytic-histiocytic
submucosal infiltrates in bowel biopsy samples. The cause is suspected to be an inappropriate or
excessive response to unidentified antigens. In some instances, a similar syndrome has been
caused by intestinal lymphosarcoma and Mycobacterium avium has been isolated from affected
bowel and mesenteric lymph nodes in a few affected horses.
Figure 5. Rectal mucosal biopsy samples
showing patchy (left) or nodular (right)
infiltration of the submucosa with
lymphocytic-histiocytic inflammatory cells
at the arrowheads, consistent with
granulomatous enteritis.
Multisystemic eosinophilic epitheliotropic disease (MEED). MEED has some similarities to GE;
however, bowel submucosal infiltrates are predominantly eosinophilic and affected horses also
commonly have nodular and ulcerative skin lesions. The latter often affect the coronary band and
may cause lameness. As with GE, the cause is suspected to be an inappropriate or excessive
response to unidentified antigens. The diagnosis is established by detecting eosinophilic infiltrates
in skin and bowel biopsies. MEED often affects the large intestine to greater extent than the small
intestine; thus, CHO absorption curve results may be normal, or peak CHO concentration may be
within the expected range but delayed in time from normal.
As with the other immune-mediated diseases, corticosteroids are the treatment of choice for GE
and MEED. The author typically uses dexamethasone starting at a dose of 0.1 mg/kg, PO or IM, q
24 h for 5-7 days with a gradually tapering dose over the next 60 days. Some horses may recover
well and corticosteroid treatment can be discontinued after 60-90 days while others may remain
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