Helicobacter pylori infection in cats and dogs:

Cats:

Of most importance in terms of widespread zoonotic potential are recent reports of H. pylori in domestic cats.

• Helicobacter pylori has been cultured or PCR-amplified from the feces, salivary secretions and dental plaque of naturally-infected cats.
• Fox et al. demonstrated multifocal gastritis in cats experimentally infected with H. pylori.
• Helicobacter pylori has been isolated from the stomachs of cats and, in one study by Handt et al., 88% of the infected cats had moderate to severe lymphofollicular gastritis.
  • Gastritis with lymphoid aggregates or follicles is typical of Helicobacter-induced gastritis in both cats and people.
  • Clinical signs of infection in cats may include chronic vomiting, weight loss and possibly diarrhea, though infections are often subclinical.
    • Diagnosis of Helicobacter-induced disease in cats can be challenging, since these organisms can be difficult to isolate and culture, and other spiral bacteria (see below) may colonize the stomachs of dogs and cats without causing disease. Demonstration of histologic evidence of inflammatory changes accompanied by spiral organisms in the mucosa may be the most reasonable approach for diagnosis in cats.
• Feline isolates of H. pylori have been shown to be genetically similar (99.7% sequence identity in 16S rRNA) to human isolates.

Dogs?

Any possible role for dogs in the epidemiology of human H. pylori infections is more tenuous. Dogs can be experimentally infected, but there is limited evidence of GI pathology in dogs. In addition, it appears that many, if not most, Helicobacter spp. recovered from naturally infected dogs are species other than H. pylori, e.g., H. bizzozeronii.

Humans to cats to humans transmission of H. pylori as a reverse zoonosis?

Helicobacter pylori infections in animals may be an example of a "reverse zoonosis." Epidemiologic studies of the relationship between H. pylori infection and animal contact are conflicting. In addition, although H. pylori has been isolated at a high frequency from commercial colony-raised research cats, the overall rate of colonization of stray cats appears to be much lower than that of humans. Thus, it is more likely that humans are the primary reservoir of the organism. In this scenario, humans transmit the organism to cats, but might cats have the potential for transmission back to humans?

Animal to human transmission of Helicobacter bizzozeronii as a true zoonosis?

Spiral bacteria that are larger and more tightly coiled than H. pylori, can be isolated very commonly from the stomachs of cats, dogs and pigs. In addition, such an organism has been isolated from 2 cats and their owner, who suffered from gastric ulcers. The human and feline isolates were indistinguishable. Recent phylogentic analyses suggest that Gastrospirillum hominis, later named H. heilmannii (the names given to the human isolate) and H. bizzozeronii (the name given to the animal isolates) are highly related, and therefore, H. bizzozeronii may be an example of a true zoonosis.

Helicobacters in other species

• Helicobacter pylori:
  • Helicobacter pylori has been detected in tissues from piglets with gastric ulcers, does not appear to be associated with the development of gastric ulcers in equine foals.
  • Helicobacter pylori has been isolated from sheep milk.
• Helicobacter mustelae:
  • This Helicobacter causes hypergastrinemia in ferrets, but is of no known zoonotic risk.
• Helicobacter acinomyx:
  • This Helicobacter has been associated with gastritis in cheetahs, but is of no known zoonotic risk.
• Intestinal Helicobacters
  • In 1998, a novel Helicobacter was isolated from kittens with severe diarrhea instead of gastric pathology, but nothing is known yet about its infectivity for humans. Intestinal Helicobacter spp. known to cause colitis in immunocompromised humans have also been isolated from dogs, but any risk for direct transmission from infected dogs or cats to humans remains to be determined.
  • Helicobacter cinaedi can be part of the normal flora of hamsters. Additionally, this Helicobacter has also been isolated from a human neonate with septicemia and meningitis. The child's mother had had contact with hamsters during her pregnancy.

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