Helicobacter Infection in Dogs
Dr. Arnold Plotnick
Culture. Growing the organism from a stomach biopsy specimen confirms the diagnosis of Helicobacter infection. Culture has a low sensitivity compared to other diagnostic methods, although in the research setting, improvements in culture techniques have increased the sensitivity of this test.
Diagnostic tests for Helicobacter can be either invasive or non-invasive. The invasive tests usually require biopsies obtained using an endoscope in a fully anesthetized animal. Non-invasive tests do not require biopsies, and the patients do not require anesthesia.
Microscopic tissue analysis. This diagnostic method is based on the visual identification of the organism in tissue specimens from the stomach. Multiple biopsy specimens from each area of the stomach should be taken due to the patchy distribution of the organism. Special stains may be necessary to help identify the organism. Failure to identify the organism in tissue specimens does not necessarily mean that the animal is not infected.
Impression smears. This technique involves dabbing a biopsy specimen onto several microscope slides, and then staining the slides and looking for the organism under the microscope. This is a fairly sensitive test and is easy to perform.
Urease test. All stomach Helicobacter species produce an enzyme called urease. Special culture tubes can be obtained that contain urea and an indicator dye. Biopsy specimens are obtained and are placed in these culture tubes. If Helicobacter is present in a biopsy specimen, the urease enzyme it produces will cleave the urea in the tube, resulting in the indicator dye changing color. This is readily visible to the eye. Positive results confirm the presence of the organism; however, other urease producing bacteria in the stomach may give a false positive result. Negative results do not necessarily mean that the animal is not infected, as different areas of the stomach are more heavily colonized than others. Also, if the animal is undergoing antibiotic therapy at the time of the test, false negative results are possible.
Electron microscopy. This technique may be used to identify Helicobacter species and differentiate between them based on their morphology (shape). This is a complicated and expensive technique, however, and its use is restricted to research facilities.
Polymerase chain reaction. This is technique that can be performed on stomach biopsy specimens that allows identification of the organism. It is the most sensitive test available for identifying the organism in a biopsy specimen. It must be kept in mind that a false negative may occur if the particular biopsy specimen does not contain any organisms, despite the fact that the animal is infected. This can happen because of the patchy distribution of the organism throughout the stomach, and emphasizes the need for multiple biopsy specimens. This test is not yet widely available.
Serology. Patients infected with Helicobacter will generate an antibody response that can be detected by analyzing the patient's serum. A recent experimental study on naturally infected dogs showed serologic testing being able to detect infection in almost 80 percent of infected dogs.
Urea breath and blood tests. For this test, the patient is given radioactively labeled urea to ingest, and Helicobacter organisms in the stomach cleave the urea with the urease enzyme they produce. The end product is ammonia and bicarbonate which is absorbed into the circulation and then exhaled in the breath as radioactive carbon dioxide. Exhaled breath is collected and analyzed. The radioactive carbon dioxide can also be analyzed in the blood rather than the breath. This test is commonly performed on people, and has been shown to be reliable for detecting naturally acquired stomach Helicobacter infections in dogs. The test is also good for monitoring response to therapy; as therapy reduces the amount of Helicobacter organisms, the amount of radioactive carbon dioxide detectable should decrease further and further.
Because there is some controversy as to whether Helicobacter infection causes any clinically significant problems in dogs, veterinarians must decide on an individual basis as to whether to treat or ignore Helicobacter infections detected by any of the methods described above. Current treatment protocols are based on those found to be effective in humans.
Antibiotics. Several antibiotics have shown activity against the organism, including amoxicillin and metronidazole, given for at least 21 days.
Antibiotics in combination with gastric acid inhibitors. Antibiotic therapy is often combined with an agent that reduces gastric acid secretion, such as famotidine (Pepcid®) or omeprazole.
Other agents. Bismuth, in the form of Pepto-Bismol, is often prescribed as part of a combination therapy protocol.
Therapy for Helicobacter infections often produces only transient results. Several studies in dogs that have evaluated combination therapy have shown that most dogs are free of the organisms three days after cessation of therapy, however, all were shown to be infected 28 days after completing therapy. It seems as if these treatment regimens, which are successful at eradicating the organism in people may only cause transient suppression rather than eradication of gastric Helicobacter species in dogs. Further studies are needed before clear guidelines regarding treatment of these infections in dogs can be formulated.
Optimal treatment for your pet requires a combination of home and professional veterinary care. Follow-up can be critical, especially if your pet does not rapidly improve. Administer all prescribed medication as directed. Alert your veterinarian if you are experiencing problems treating your pet.
Because Helicobacter infections cause significant disease in humans, attempts at developing a vaccination have been made. An oral vaccination has been successful in preventing and treating Helicobacter infections in mice, and much research is being conducted to try to develop a successful vaccine for humans. As the relationship between Helicobacter organisms and disease in companion animals becomes clearer, a similar vaccine may be desirable and available for cats and dogs.