Helicobacter (H.) spp. are helical or curved, gram-negative bacteria. At least 35 species are known; some of them colonise the gastric mucosa, while others colonise the intestine and liver of humans or animals. Transmission occurs via the oral-oral or possibly also the anal-oral route. In humans, H. pylori is correlated with gastritis and stomach ulcers and can also be transmitted to animals. However, it is not pathognomonic in dogs.
Pathogenicity of Helicobacter spp. in animals has not yet completely been clarified. Infections do not always cause a disease; prevalence is very high in both healthy as well as infected animals. H. mustelae was detected in ferrets with gastritis and stomach ulcers, H. heilmanii was found in pigs with stomach ulcers. They are also associated with gastritis, vomiting and inappetence in dogs, cats and ferrets. In cats, Helicobacter spp. Are associated with progressive lymphocytic cholangitis. In Muridae, helicobacter infection is often seen in association with typhlitis or rectal prolapse. In hamsters, the infection is often subclinical. In some cases, gastritis similar to that in humans may occur.
Gastric Helicobacter spp. include, H. heilmannii, H. felis, H. bizzozeronii, H. salomonis and others; the intestinal ones comprise, for example, H. canis, H. bilis, H. cinaedi as well as Flexispira rappini. Flexispira rappini, which is also assigned to the genus Helicobacter, is associated with abortions in sheep. Aborted lambs show multifocal hepatic necroses – similar to campylobacter infections.