Bacteriophages are a better indicator of illness rates than bacteria amongst users of a white water course fed by a lowland river

Abstract

An examination was made of the risk factors for gastrointestinal illness (GI) and other symptoms among canoeists and rafters using an artificial white-water canoe slalom course fed by a lowland river. The investigation was made by carrying out cohort studies of users on several days throughout one year. On each day water samples were collected for the determination of Escherichia coli, enterococci (faecal streptococci), F-specific RNA bacteriophage, sulphite reducing clostridia, culturable enteroviruses and turbidity. Of 755 questionnaires distributed, 473 (63%) were returned. The relative risks of GI and other symptoms were determined by logistic regression analyses. The variables associated with an increased risk of GI-illness were swallowing water, unintentional swimming in the course, eating and drinking before getting changed and the levels of F-specific RNA bacteriophages. Being a regular user was associated with a decreased risk of GI-illness. This study demonstrates the value of F-specific RNA bacteriophages as an index of risk from recreational use of a fresh water environment.