A conceptual model of water's role as a reservoir in Helicobacter pylori transmission: a review of the evidence

Abstract

Helicobacter pylori infection plays a role in the development of chronic gastritis, peptic ulcer and gastric cancer, yet the route of transmission into susceptible hosts remains unknown. Studies employing microbiological techniques have demonstrated that H. pylori has the ability to survive when introduced into water and that H. pylori is present in water and other environmental samples all over the world. Epidemiological studies have shown that water source and exposures related to water supply, including factors related to sewage disposal and exposure to animals, are risk factors for infection. This review describes the microbiological and epidemiological evidence for, and proposes a model of, waterborne H. pylori transmission outlining important features in the transmission cycle. In the model, humans and animals shed the bacteria in their faeces and the mechanisms for entry into water, and for survival, ingestion and infection are dependent upon a range of environmental influences. Verification of the proposed model pathways has important implications for public-health prevention strategies.

Fig. 1

Methods of H. pylori detection. ––––, Strong evidence in published literature; , some evidence in published literature; ………, insufficient evidence.

Fig. 2

Conceptual model of waterborne H. pylori transmission pathways. , Long-term host; , short-term reservoir; –––, transmission pathway; , reduced transmission probability pathway.