Helicobacter Infection in Dogs
Overview of Canine Helicobacter Infection
Helicobacter is a stomach-associated spiral shaped bacterium that has been linked to peptic ulcer disease and cancer in humans. The organism can be isolated from the stomach of some cats and dogs, but whether it induces any disease is controversial.
The organism is found in a large percentage of normal healthy dogs, vomiting dogs, research laboratory dogs and animal shelter dogs. The organism has been isolated from other species besides dogs and humans, such as cats, pigs, cheetahs, ferrets and non-human primates.
In a majority of cases, infection of dogs with helicobacter is not accompanied by clinical signs. In a few cases, infection leads to mild gastritis (stomach inflammation).
What To Watch For
- Occasional vomiting
- Poor appetite
Diagnosis of Helicobacter Infection in Dogs
- Microscopic tissue analysis
- Impression smears
- Urease test
- Electron microscopy
- Polymerase chain reaction
- Urea breath and blood test
Treatment for Dogs with Helicobacter Infection
- Antibiotics in combination with gastric acid inhibitors
- Other agents
Home Care and Prevention for Dogs with a Helicobacter Infection
Administer all prescribed medications and carefully monitor your pet for vomiting or a poor appetite.
Information In-depth on Helicobacter Infection in Dogs
Helicobacter is a gastric spiral bacterium that has been linked to peptic ulcer disease in humans. It has also been declared a carcinogen (cancer causing agent) in humans due to its association with stomach cancers such as adenocarcinoma and lymphoma. While much is known about the organism and its clinical consequences in people, comparatively little is known about infection in dogs and cats, and it is still unclear as to whether any diseases can be attributed to these bacteria.
In the late 1800s, gastric spiral organisms were first described in humans and in animals. The discoveries demonstrated that it was possible that the highly acidic stomach, which had until that point been considered sterile, was capable of harboring a population of bacteria.
About 100 years later, interest in gastric spiral organisms was re-ignited when an association between these organisms and gastric ulcers was discovered in humans. Soon afterward, similar bacteria were isolated from the stomachs of ferrets, nonhuman primates, dogs, cats, pigs and cheetahs.
Gastric helicobacter organisms are highly prevalent in dogs. They have been identified in 61 to 82 percent of dogs that are brought to a veterinarian for vomiting; in 67 to 86 percent of clinically normal, healthy pet dogs; and approaching 100 percent of laboratory beagles and shelter dogs. Several different species of Helicobacter have been isolated from the dog, and simultaneous infection with more than one species seems to be common.
Exactly how the organism is transmitted is not clear. In people, fecal-oral spread has been hypothesized because the organism can be cultured from feces. Oral-oral spread is suggested because the organism can be found in the saliva of infected people. Recently the organism was isolated in surface water in the United States and Sweden. Similar studies have not been performed for species of the organism that can infect dogs, thus, some or perhaps all of the modes suggested for humans are possible for dogs. In dogs, transmission of the organism from a mother to her puppies has been reported.
There is some concern about the risk of transmission of Helicobacter-like organisms from dogs and cats to humans, as some species of Helicobacter that infect humans have been found in cats and dogs. The risk seems relatively slight, however.
The role of Helicobacter in causing gastric disease in dogs is hotly debated. The majority of infected dogs do not show obvious clinical signs of gastric disease. This is in stark contrast to humans, for whom strong evidence links the organism to chronic gastritis, ulcer disease and stomach cancers. The organism has been implicated in causing gastric ulcers in ferrets and pigs, and in causing severe gastritis (stomach inflammation) in cheetahs.
Diagnosis In-depth of Helicobacter Infection in Dogs
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.
- 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.
- 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.
Therapy In-depth for Dogs with a Helicobacter Infection
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.
Follow-up Care for Dogs with a Helicobacter Infection
Optimal treatment for your dog requires a combination of home and professional veterinary care. Follow-up can be critical, especially if your dog does not rapidly improve. Administer all prescribed medication as directed. Alert your veterinarian if you are experiencing problems treating your dog.
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.