IBD's Cause: 'The Million-Dollar Question'

The bowel disease may result from an overreaction to normal bacteria

by Margaret H. Bonham
Reprinted with permission from Your Dog, Tufts University
Copyright 2005, Tufts University

Indy, a 2-year-old German Shepherd Dog, was having another bout of diarrhea. She's had it since she contracted Clostridium perfringens, an intestinal bacterial infection, as a puppy. In fact, said owner Karen Holowinski of Denver, Cob., "She gets these bad episodes of diarrhea every other month."

Indy might not simply have a Clostridial infection, however. Its recurrence could be a sign of a more serious condition called inflammatory bowel disease, which is not to be confused with the human condition, irritable bowel syndrome. IBD is a disease in which the digestive tract has an immune reaction to normal bacteria in it and becomes inflamed. The afflicted dog may suffer chronic diarrhea, vomiting and weight loss. The disorder may be treated but not cured.

"Inflammatory bowel disease is thought to represent an overreaction to the presence of normal bacteria in the intestine," said Michael Stone, DVM, clinical assistant professor at the Cummings School of Veterinary Medicine at Tufts University. "Recurrent, waxing and waning clinical signs are considered IBD's hallmark."

Serious Consequences

The mean age for dogs developing IBD is 6 years, but those younger than 2 years of age have been diagnosed. If untreated, IBD can have serious consequences. In Soft Coated Wheaten Terriers, for example, it's a precursor for protein-losing enteropathy and protein-losing nephropathy, diseases that cause significant protein losses in dogs. Other breeds prone to proteinlosing enteropathy include Basenjis, Shar-Peis, Norwegian Lundehunds and Yorkshire Terriers.

The cause of IBD? "That's the million-dollar question," said Cohn Burrows, DVM, BVetmed, Ph.D., MRCVS, at the University of Florida College of Veterinary Medicine in Gainesville.

In an IBD-susceptible patient, the immune response of the intestine goes into overdrive. Dr. Burrows, a specialist in internal medicine and chair of Small Animal Veterinary Medicine, offers his students a comparison, telling them it's as though five years ago a dog who was a patient bit him in the arm. "Then three years ago, I got stuck with a nail on the same arm. If you look at the scar tissue under the microscope, you'll see the scar, but you won't he able to tell what caused it - the dog bite or the nail. It looks the same. That's how IBD is.

Tika

"About 30 percent of dogs have either diarrhea or vomiting alone," Dr. Burrows said. "It may involve the stomach, small intestine or colon. There may be inflammation in one or all three."

Some types of intestinal disease, such as lymphocytic-plasmacytic enterocolitis, have a genetic predisposition. Soft Coated Wheaten Terriers, Basenjis, Lundehunds, German Shepherd Dogs and, in the United Kingdom, Golden Retrievers may be predisposed.

Veterinarians identify the type of IBD through an intestinal biopsy, 'which may he performed through surgery or an endoscopic examination. One classification for inflammatory bowel disease uses the predominant cell type involved. Among them:

Eosinophilic gastroenteritis an infiltration of white blood cells in the stomach or intestine. It's seen predominantly in Rottweilers.
Histiocytic ulcerative colitis - a severe form of IBD seen only in Boxers. The inflammatory cells, or histiocytes, infiltrate the intestinal wall. Recent studies have demonstrated that this form responds to antibiotics.
Eosinophilic enterocolitis thought to be associated with food allergies or parasite infection.
Granulomatous enteritis - a very uncommon form of disease in dogs, similar to Crohn's disease in humans.
Neutrophilic and lymphoplasmacytic enterocolitis - the most common forms of disease and unfortunately, of undetermined cause.

"Treatment for IBD involves accurately excluding all possible causes for inflammation of the intestine and toning down the immune system," said Dr. Stone, a specialist in internal medicine. "To exclude known causes of intestinal inflammation, many veterinarians consider these the minimum steps: blood work, fecal analysis, de-worming and dietary trials with novel - never before ingested - ingredients. To tone down the immune system, prednisone and other drugs may be used."

Veterinarians may prescribe immunosuppressants and antibiotics to reduce bacteria in the intestines.

Food Intolerance

Most veterinarians opt for a bland diet that won't aggravate IBD. "The best diet for IBD isn't known," said Dr. Stone. "If a patient responds to a change of diet, then he doesn't have IBD. He has more accurately food intolerance. I tend to use a bland diet initially for patients with true IBD along with drug therapy. If food intolerance hasn't been excluded, I'll frequently start with a novel ingredient diet before reaching for drugs. The best novel ingredient diet depends upon which diets have been previously fed to that patient, so an accurate dietary history is essential."

Novel ingredients include fish, venison and kangaroo for a protein source and potatoes, barley or other grains for carbohydrates. Dr. Burrows recommends going with a single novel protein source or switching to a prescription allergy diet available from many pet food manufacturers through veterinarians.

Because the cause of IBD hasn't been determined, it's impossible to suggest ways to prevent it. In some cases, IBD may simply be genetic. Preventing your dog from scavenging is helpful but not always practical. You can store trash behind a cupboard or closet at home, but if your dog is a vacuum cleaner while walking outdoors, he may pick up food wrappers - or worse - and swallow them before you can stop him.

Although IBD can't be cured, the encouraging news is that, with proper diagnosis and treatment, this chronic illness can be successfully managed in most cases.

Holowinski took her dog, Indy, to the veterinarian who put her on two antibiotics and a novel protein diet. After eight weeks, the veterinarian will evaluate her to decide if more testing is needed.

"Waxing and waning clinical signs are considered IBD's hallmark."

Researchers Seek Causes and Treatments of the Disease

The Morris Animal Foundation is funding several studies to determine the causes and treatments of inflammatory bowel disease.

At the University of Minnesota, Robert Washabau, DVM, professor of Veterinary Clinical Sciences and department chair, is in the first year of a two-year study of inflammatory molecules, or cytokines, and the immune response in IBD. He hopes to identify similar inflammatory responses that will enable veterinarians develop treatments. The current findings look promising, Dr. Washabau said, and he wants to enroll 50 more dogs in the study. If interested, please contact him at washabau@umn.edu.

At the University of Pennsylvania, Peter J. Felsburg, VIVID, Ph.D., is examining cells from the intestinal lining to determine the role they play in IBD.

At the University of Washington, Bonnie Grambow Campbell, DVM, Ph.D., is studying abnormal trefoil peptide levels, which are secreted in gastrointestinal tract inflammation. Investigators will compare the levels in normal, inflamed and cancerous canine tissues to determine if the findings can diagnose IBD or cancer.

"Most veterinarians opt for a bland diet that won't aggravate IBD."

If Stomach Upset Doesn't Improve by Day 2, It's Time for a Veterinary Visit

Diarrhea and vomiting aren't usually a big cause for concern. You can treat mild diarrhea with either a kaolin product - an absorbent - or bismuth subsalicylate, found in Pepto-Bismol. Ask your veterinarian for the proper dosages. However in the vast majority of cases, upset stomachs in the dog resolve within one to two days without specific treatment.

Take your dog for prompt veterinary treatment if:

Herefuses to eat.
Diarrhea is bloody or black.
He's becoming dehydrated. Check the gums - sticky gums are a sign of severe dehydration.
Diarrhea or vomiting is in association with a fever - more than 102.5 degrees Fahrenheit.
The dog vomits blood or black coffee-ground like substances.