Quantitative microbial risk assessment with microbial source tracking for mixed fecal sources contaminating recreational river waters, Iowa, USA

Environmental Science & Technology Water
By: , and 

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Abstract

Fecal contamination of surface water can cause acute gastrointestinal illness (AGI) among recreators. AGI risk varies among human, livestock, and wildlife fecal sources, but the prevalence of individual sources is unknown for most recreational sites. We estimated AGI risk for six sites near Des Moines, Iowa, using quantitative microbial risk assessment combined with microbial source-tracking (MST). Water samples (n = 147) collected over two years were tested for 36 qPCR assays quantifying waterborne pathogens and MST markers specific to avian, bovine, human, and porcine fecal sources. Average swimming risk across all sites was 5 (95% CI: 0.0030–142) to 67 (16–215) AGI cases per 1,000 recreators. Individual fecal sources were rarely associated with swimming exposures where risk was >36 AGI cases per 1,000 recreators; most high-risk exposures were associated with simultaneous occurrence of multiple fecal sources. Iowa’s beach action value for Escherichia coli (235 MPN/100 mL) identified >90% of high-risk exposures at five of six sites, so was generally protective of public health in this setting. For sites influenced by mixed fecal sources, results illustrate that identifying a single dominant source of risk is less important than recognizing the number of unique fecal sources that impact AGI risk.

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Publication type Article
Publication Subtype Journal Article
Title Quantitative microbial risk assessment with microbial source tracking for mixed fecal sources contaminating recreational river waters, Iowa, USA
Series title Environmental Science & Technology Water
DOI 10.1021/acsestwater.3c00652
Volume 4
Issue 7
Year Published 2024
Language English
Publisher American Chemical Society
Contributing office(s) Upper Midwest Water Science Center
Description 14 p.
First page 2789
Last page 2802
Country United States
State Iowa
City Des Moines
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