Integrating bacterial and viral water quality assessment to predict swimming-associated illness at a freshwater beach: a cohort study

PLoS One. 2014 Nov 19;9(11):e112029. doi: 10.1371/journal.pone.0112029. eCollection 2014.

Abstract

Background & objective: Recreational waters impacted by fecal contamination have been linked to gastrointestinal illness in swimmer populations. To date, few epidemiologic studies examine the risk for swimming-related illnesses based upon simultaneous exposure to more than one microbial surrogate (e.g. culturable E. coli densities, genetic markers). We addressed this research gap by investigating the association between swimming-related illness frequency and water quality determined from multiple bacterial and viral genetic markers.

Methods: Viral and bacterial genetic marker densities were determined from beach water samples collected over 23 weekend days and were quantified using quantitative polymerase chain reaction (qPCR). These genetic marker data were paired with previously determined human exposure data gathered as part of a cohort study carried out among beach users at East Fork Lake in Ohio, USA in 2009. Using previously unavailable genetic marker data in logistic regression models, single- and multi-marker/multi-water quality indicator approaches for predicting swimming-related illness were evaluated for associations with swimming-associated gastrointestinal illness.

Results: Data pertaining to genetic marker exposure and 8- or 9-day health outcomes were available for a total of 600 healthy susceptible swimmers, and with this population we observed a significant positive association between human adenovirus (HAdV) exposure and diarrhea (odds ratio = 1.6; 95% confidence interval: 1.1-2.3) as well as gastrointestinal illness (OR = 1.5; 95% CI: 1.0-2.2) upon adjusting for culturable E. coli densities in multivariable models. No significant associations between bacterial genetic markers and swimming-associated illness were observed.

Conclusions: This study provides evidence that a combined measure of recreational water quality that simultaneously considers both bacterial and viral densities, particularly HAdV, may improve prediction of disease risk than a measure of a single agent in a beach environment likely influenced by nonpoint source human fecal contamination.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenoviruses, Human / genetics
  • Adenoviruses, Human / isolation & purification*
  • Adolescent
  • Adult
  • Child
  • Child, Preschool
  • Cohort Studies
  • Diarrhea / microbiology*
  • Diarrhea / virology
  • Escherichia coli / genetics
  • Escherichia coli / isolation & purification*
  • Female
  • Gastrointestinal Diseases / microbiology*
  • Gastrointestinal Diseases / virology
  • Genetic Markers
  • Humans
  • Lakes / microbiology*
  • Lakes / virology
  • Male
  • Middle Aged
  • Swimming
  • Water Quality / standards*
  • Young Adult

Substances

  • Genetic Markers

Grants and funding

This study was funded by the Public Health Preparedness for Infectious Diseases program (http://phpid.osu.edu) and The Ohio State University Targeted Investment in Excellence program sponsored by the Offices of Academic Affairs, the President, and Research. The human health and exposure data collection effort was funded by the Ohio Water Development Authority. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.