Page 680 - Veterinary Immunology, 10th Edition

VetBooks.ir Inflammatory Bowel Diseases

Chronic enteropathies with persistent clinical signs in domestic
species are a diverse group of diseases that result from a

combination of genetic, microbial, nutritional, allergic, and
environmental factors. Some resemble inflammatory bowel diseases
in humans (Crohn's disease and ulcerative colitis) but most cases
probably have a very different pathogenesis. Some result from
dysbiosis and dysregulation of the immune responses to the

intestinal microbiota. As pointed out, commensal bacteria within
the intestine are prevented from invading the intestinal wall by a
glycocalyx, by high concentrations of defensins, and by an ongoing

IgA response. They also suppress inflammation by blocking NF-κB
activation and generating IL-10–secreting Treg cells. If these control
mechanisms fail and the animal responds aggressively to its
commensals, perhaps by increasing Th1 responses, then severe
inflammation may result, making the intestine much more

susceptible to bacteria-induced injury.
Canine chronic enteropathies are characterized by persistent or
recurrent gastrointestinal inflammation of undetermined cause.

These diseases present with a history of chronic vomiting, diarrhea,
and weight loss. There is a breed predisposition in Weimaraners,
Rottweilers, German Shepherds, Border Collies, and Boxers. The
most common form is a lymphocytic-plasmacytic enteritis.
Affected dogs may show an increase in Proteobacteria, especially

E. coli or Pseudomonas, and a decrease in Firmicutes and
Bacteroidetes. Other changes, such as increased bacterial adherence
to the mucosa, reduced bacterial diversity, changes in the bacterial

mixture, and overgrowth of other bacteria, may all contribute to the
inflammation (see Fig. 21.4).
Many cases are associated with an increase in T cell and IgA +
plasma cells in the small intestine. The T cells are primarily α/β
+
CD4 cells, although there is an increase in intraepithelial γ/δ T cells
as well. There may also be an increase in the numbers of intestinal
mast cells. Some dogs with chronic enteropathy have reduced IgA
levels in feces, duodenum, and blood. Hypoalbuminemia may

reflect severe protein loss and carries a poor prognosis.

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