HELICOBACTER INFECTIONS

STEPHANIE SPECK

Bundeswehr Institute of Microbiology, Department of Virol­ogy and Rickettsiology, Munich, Germany

Helicobacter infections are reported from mammals and birds, and mainly infect the stomach, intestine, liver and gallbladder.

Helicobacter organisms are small (0.5—1.0 μm in width, 2.5-4.0 μm in length), curved, microaerophilic Gram­negative rods, which are motile by several sheathed flagella. More than 40 candidate and definitive species of Helico­bacter have been described, and all occur in the gastroin­testinal tract of humans and animals worldwide. Genera closely related to Helicobacter are Wolinella, Flexispira, Campylobacter and Arcobacter.

Helicobacter spp. have been described in various captive wild, domestic, laboratory animal and pet species, but little information is available on the occurrence of Heli­cobacter and associated disease in wild animals. Helico­bacter hepaticus and H. bilis are mouse pathogens frequently affecting laboratory mice colonies, where they colonize the liver and cause hepatitis. Helicobacter hepaticus- induced lesions may progress to hepatocellular tumours. Helicobacter pylori causes chronic gastritis and gastric cancer in humans. In free-living wild animals worldwide, Helicobacter spp. infection has been described in carnivores, marine mammals and birds. In European wildlife, Helicobacter and Helicobacter-like organisms (HLO) have been observed in free-ranging red foxes (Vulpes vulpesf"'¹2 and lynx (Lynx lynxf¹2. The gastric mucosa from 17 of 25 (68%) lynx and from three of four (75%) red foxes was positive for Helicobacter spp. by polymerase chain reaction (PCR) in a Swedish study. Phylogenetic analysis grouped these Helicobacter into a cluster including ⁱCandidatus H. heilmannii', H.

Pathogenesis and virulence factors in H. pylors have been studied intensively because of its pathogenic role in humans. In domestic animals, in particular pigs, gastric ulcers have been linked to Helicobacter spp. infection, but the exact role of the bacteria in the development of lesions is not clear. None of the lynx and red foxes investigated in the Swedish study showed macroscopic lesions in the stomach or liver(¹²). Chronic gastritis characterized by focal lympho-plasmacytic cellular infiltration was reported in 11 of 44 HLO-positive red foxes(¹⁰). HLO infection in Turkish red foxes was associated with chronic mild or moderate inflammatory changes but without any correla­tion between the presence or density of bacteria and gastric inflammation⁽¹¹⁾.

Most Helicobacter spp. are carried by animals and humans without causing apparent disease. Clinical signs in animals include vomiting, diarrhoea and weight loss, but have not been described in wildlife.

The isolation and identification of Helicobacter spp. is difficult and is not attempted in most veterinary diagnostic laboratories. Scrapings of the gastric mucosa might be examined microscopically for the presence of motile, helical-shaped organisms. Alternatively, the organisms may be visualized on histologic sections prepared with silver stain (a method non-specific for Helicobacter spp.) or by immunofluorescence or immunoperoxidase methods. Preparations may also be examined by electron micros­copy. Most of the Helicobacter species considered as patho­genic produce urease, which can be tested for on biopsy specimens. Assays for the detection of antigen and anti­bodies are available. PCR requires tests for several house­keeping genes to identify Helicobacter on a species level⁽¹⁴⁾.

The zoonotic potential of the Helicobacter species found in wild animals in Europe is not clear.