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ARS Home » Midwest Area » Madison, Wisconsin » U.S. Dairy Forage Research Center » Environmentally Integrated Dairy Management Research » Research » Publications at this Location » Publication #418037
Research Project: Managing Nutrients and Assessing Pathogen Emission Risks for Sustainable Dairy Production Systems

Location: Environmentally Integrated Dairy Management Research

Title: Source-tracking health risk from waterborne human and zoonotic pathogens during recreational water use

Author
item Burch, Tucker
item STOKDYK, JOEL - Us Geological Survey (USGS)
item FIRNSTAHL, AARON - Us Geological Survey (USGS)
item Opelt, Sarah
item Cook, Rachel
item Heffron, Joseph
item BROWN, AMANDA - Polk County Conservation
item HRUBY, CLAIRE - Drake University
item Borchardt, Mark

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 11/22/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical 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 impact of individual sources on AGI risk is unknown for most recreational sites. We estimated AGI risk for six sites in the Des Moines, Iowa, metropolitan area using quantitative microbial risk assessment (QMRA) 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 sites varied from 5 to 67 AGI cases per 1,000 recreators. Average swimming risk for two sites exceeded USEPA’s 2012 risk benchmark of 36 AGI cases per 1,000 recreators, while risk estimates for other sites and limited contact activities (e.g., kayaking, fishing) were generally below the benchmark. QMRA results were also examined relative to the occurrence of MST markers, and we found that most swimming exposures with risk >36 AGI cases per 1,000 recreators were associated with simultaneous exposure to multiple fecal sources; individual fecal sources were rarely associated with high-risk exposures on their own. Iowa’s primary contact recreation standard for Escherichia coli (235 MPN/100mL) identified >90% of high-risk exposures at five of six sites, so was generally protective of public health in this setting. However, as a non-source-specific fecal indicator, Escherichia coli could not identify the fecal sources that contributed to AGI risk. By combining MST with QMRA, results illustrate that wildlife and/or livestock fecal sources can contribute significantly to risk even in an urban environment. Furthermore, identifying a single dominant source of risk may be less important than recognizing the number of unique fecal sources that impact AGI risk at a given site.