The use of faecal indicator organisms to manage microbial health risks in recreational waterways not impacted by point sources of sewage: a systematic review of the epidemiological evidence.

This PRISMA review investigated the extent to which epidemiological evidence supports the use of faecal indicator organisms (FIOs) to manage microbial health risks in recreational waters without point sources of sewage. The quality of papers meeting the inclusion criteria was appraised using the Office of Health Assessment and Translation (OHAT) Risk of Bias tool and low-bias studies were synthesised. Studies consistently reported elevated illness risks (particularly gastrointestinal) among bathers compared with non-bathers. However, no FIOs or pathogens were associated consistently with any health outcomes. While enterococci most frequently correlated with a variety of illnesses, the relatively even split of positive and negative associations suggests an overall lack of association. Consequently, applying FIO guidelines derived from epidemiological studies with point sources of sewage could result in type I and type II errors. Overall, results suggest that the sources and drivers of health risks are site-specific. Tools including sanitary surveys, microbial source tracking, epidemiology and quantitative microbial risk assessment provide avenues for characterising site-specific health risks, for those who can afford them. Meanwhile, characterising the site-specific sources/drivers of contamination seems pragmatic as the limited evidence so far suggests that FIO monitoring may not be sufficient to protect health in these waters.