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Find information on animal health topics, written for the veterinary professional.

Disorders Caused by Bacteria in the Digestive System of Dogs

By Dana G. Allen, DVM, MSc, DACVIM, Professor and Chair, Department of Clinical Studies, Ontario Veterinary College, University of Guelph ; Lisa E. Moore, DVM, DACVIM ; Carlton L. Gyles, DVM, PhD, Professor Emeritus, Department of Pathobiology, Ontario Veterinary College, University of Guelph ; Sharon Patton, MS, PhD, Professor of Parasitology, Department of Biomedical and Diagnostic Sciences, College of Veterinary Medicine, University of Tennessee ; Andrew S. Peregrine, BVMS, PhD, DVM, DEVPC, DACVM, Associate Professor, Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada ; Thomas W. Swerczek, DVM, PhD, Professor, Department of Veterinary Science, University of Kentucky ; Ben H. Colmery, DVM, DAVDC ; James G. Fox, DVM, MS, DACLAM, Professor and Director, Division of Comparative Medicine, Massachusetts Institute of Technology ; H. Carolien Rutgers, DVM, MS, DACVIM, DECVIM-CA, DSAM, MRCVS, Senior Lecturer, The Royal Veterinary College, University of London ; Jörg M. Steiner, DrMedVet, PhD, DACVIM, DECVIM-CA, AGAF, Associate Professor and Director, Gastrointestinal Laboratory, Department of Small Animal Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Texas A & M University ; Sofie Muylle, DVM, PhD, Faculty of Veterinary Medicine, Department of Morphology, Ghent University ; Walter Ingwersen, DVM, DVSc, DACVIM, Specialist, Companion Animals, Boehringer Ingelheim (Canada) Ltd, Vetmedica ; Stanley I. Rubin, DVM, MS, DACVIM, Clinical Professor, Department of Veterinary Clinical Medicine, College of Veterinary Medicine, University of Illinois at Urbana-Champaign ; Sharon Campbell, DVM, MS, DACVIM, Manager, Pharmacovigilance Regulatory Affairs, Veterinary Medicine Research and Development, Pfizer Inc.

Certain bacteria may cause gastrointestinal disease in dogs. The most common of these are discussed below.

Campylobacter Infection

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Gastrointestinal campylobacteriosis is a bacterial disease. It is caused by 2 related bacteria of the Campylobacter genus. These organisms, along with a number of other species of Campylobacter, can be isolated from infected dogs that do not show signs of infection (carriers) as well as from dogs that show signs of the illness. This disease can be transmitted to humans. Animals, including dogs (especially those recently adopted from shelters), and wild animals maintained in captivity can serve as sources of human infection.

Exposure to feces of infected animals and food or waterborne transmission appear to be the most common routes of infection. One suspected source of infection for pets is eating undercooked poultry and other raw meat products. Wild birds also may be important sources of water contamination.

The diarrhea appears to be most severe in young dogs. Typical signs include mucus-laden, watery, or bile-streaked diarrhea (with or without blood) that lasts 3 to 7 days; reduced appetite; and occasional vomiting. Fever may also be present. Intermittent diarrhea may persist for more than 2 weeks; in some, the intermittent diarrhea may continue for months. To diagnose campylobacteriosis, a veterinarian will test the animal’s feces and blood for evidence of infection.

Antibiotic treatment for dogs found to carry these bacteria is usually reserved for those that are young, severely affected, or a potential source of human infection. This is because other organisms are likely to be involved and antibiotic treatment is often not effective.

Helicobacter Infection

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In humans, Helicobacter pylori bacteria have been associated with stomach inflammation, ulcers, and gastric adenocarcinoma. Although H. pylori has not been found in dogs, several other species of Helicobacter have been isolated. So far, the evidence suggests that the bacteria cause a mild inflammation that has no signs. Whether their presence predisposes the infected animal to food allergies, inflammatory bowel disease, ulcers, or cancer is not yet known. In dogs, the bacteria have been associated with occasional vomiting.

Several tests, including biopsy of the stomach lining, may be used by your veterinarian to diagnose the presence of the bacteria. Confirming the diagnosis requires culturing the bacteria in a laboratory. Several types of antibiotics have been used to treat the infection in dogs. In many cases, however, the bacteria recur. Whether this is due to reinfection or failure of the antibiotics to completely eliminate them following treatment is not known.

Salmonella Infection

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Many species of Salmonella bacteria can cause gastrointestinal illness. A Salmonella infection can cause severe blood poisoning (septicemia) or inflammation of the intestine. The disease is infrequent in dogs. Infected dogs may become carriers of Salmonella but often do not show any signs of disease.

When disease is seen, it is often associated with hospitalization, another infection or disease in adult dogs, or exposure to large numbers of the bacteria in puppies. Signs include sudden diarrhea and blood poisoning. Pneumonia may be evident. Salmonella infection is likely to cause miscarriage in pregnant dogs. Diagnosis is based on signs of disease and on the laboratory examination of feces.

Early treatment is essential for blood poisoning. In many cases, antibiotics are given intravenously. Fluids may be given intravenously as well. The intestinal form of the disease is difficult to treat effectively. Antibiotics are not always rec-ommended, due to concerns about the development of antibiotic resistant bacteria, as well as concerns about the effects of antibiotics on normal intestinal bac-teria of dogs. Although the signs of disease may disappear, eliminating the bacteria from the body is difficult, particularly in adult dogs.

Because of the above problems, it is particularly important to follow your veterinarian’s directions carefully if your pet is infected with Salmonella. The medication selected and both the timing of the doses and the duration of treatment are important in eliminating the infection.

Salmonella can be transmitted from dogs to humans, so care should be taken to avoid contact with feces from an infected dog.

Tyzzer Disease

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Tyzzer disease is an infection caused by the bacterium Clostridium piliforme. It affects a wide range of animals; however, the disease is rare in dogs. Infection most likely results from oral exposure to infective spores from the environment or contact with carrier animals. The bacteria primarily affect cells in the intestine, liver, and heart. The disease most often affects young, healthy animals that are subjected to stress. In some species, the disease occurs along with other diseases, such as distemper and mycotic pneumonia in dogs.

Signs vary, but may include decreased activity, loss of appetite, fever, jaundice, and diarrhea. Before death, there are convulsions and coma. A diagnosis of Tyzzer disease is based on laboratory examination of tissue samples for the presence of the bacteria. Little is known about the effectiveness of antibiotics for treatment; some antibiotics are known to aggravate the disease. Dogs suspected of being infected may be treated with intravenous fluids and appropriate antibiotics.