Viral, bacterial, and protozoan pathogens and fecal markers in wells supplying groundwater to public water systems in Minnesota, USA

Environ Health Perspect

Kieke

et al. 2021

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BACKGROUND: Groundwater quality in the Silurian dolomite aquifer in northeastern Wisconsin, USA, has become contentious as dairy farms and exurban development expand. OBJECTIVES: We investigated private household wells in the region, determining the extent, sources, and risk factors of nitrate and microbial contamination. METHODS: Total coliforms, Escherichia coli, and nitrate were evaluated by synoptic sampling during groundwater recharge and no-recharge periods. Additional seasonal sampling measured genetic markers of human and bovine fecal-associated microbes and enteric zoonotic pathogens. We constructed multivariable regression models of detection probability (log-binomial) and concentration (gamma) for each contaminant to identify risk factors related to land use, precipitation, hydrogeology, and well construction. RESULTS: Total coliforms and nitrate were strongly associated with depth-to-bedrock at well sites and nearby agricultural land use, but not septic systems. Both human wastewater and cattle manure contributed to well contamination. Rotavirus group A, Cryptosporidium, and Salmonella were the most frequently detected pathogens. Wells positive for human fecal markers were associated with depth-to-groundwater and number of septic system drainfield within 229 m. Manure-contaminated wells were associated with groundwater recharge and the area size of nearby agricultural land. Wells positive for any fecal-associated microbe, regardless of source, were associated with septic system density and manure storage proximity modified by bedrock depth. Well construction was generally not related to contamination, indicating land use, groundwater recharge, and bedrock depth were the most important risk factors. DISCUSSION: These findings may inform policies to minimize contamination of the Silurian dolomite aquifer, a major water supply for the U.S. and Canadian Great Lakes region.

Section: Microbial Source Tracking and Pathogen Occurrencementioning

confidence: 99%

Sources and Risk Factors for Nitrate and Microbial Contamination of Private Household Wells in the Fractured Dolomite Aquifer of Northeastern Wisconsin

Borchardt

Environ Health Perspect

Kieke

et al. 2021

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“…Similarly, values for protozoan pathogens (all Cryptosporidium types and G. duodenalis) were extrapolated from published comparisons of qPCR and immunofluorescent antibody (IFA) measurements collected in groundwater from Minnesota (Stokdyk et al 2019(Stokdyk et al , 2020. Finally, the value of H for adenovirus was based on Kundu et al (2013) because it is the most widely used value in the QMRA literature.…”

Section: Exposure Assessmentmentioning

confidence: 99%

“…0 (0, 0) 0 (0, 0) 0 (0, 0) 60 (0, 470) 0 (0, 0) 0 (0, 0) 60 (0, 470) Giardia duodenalis 0 (0, 0) 0 (0, 0) 0 (0, 10) 0 (0, 0) 0 (0, 0) 0 (0, 40) 0 ( 0 consideration in the current QMRA. QMRAs that rely on published pathogen measurements may misrepresent risk or etiologies because some pathogens are underrepresented in the groundwater literature (Stokdyk et al 2019(Stokdyk et al , 2020. Because the expected etiologies for waterborne AGI have implications for water management, like treatment and mitigation strategies, sitespecific exposure assessments can contribute to efficient and effective groundwater management.…”

Section: Total By Pathogen Pathogenmentioning

confidence: 99%

Quantitative Microbial Risk Assessment for Contaminated Private Wells in the Fractured Dolomite Aquifer of Kewaunee County, Wisconsin

Burch

Environ Health Perspect

Spencer

et al. 2021

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BACKGROUND: Private wells are an important source of drinking water in Kewaunee County, Wisconsin. Due to the region's fractured dolomite aquifer, these wells are vulnerable to contamination by human and zoonotic gastrointestinal pathogens originating from land-applied cattle manure and private septic systems. OBJECTIVE: We determined the magnitude of the health burden associated with contamination of private wells in Kewaunee County by feces-borne gastrointestinal pathogens. METHODS: This study used data from a year-long countywide pathogen occurrence study as inputs into a quantitative microbial risk assessment (QMRA) to predict the total cases of acute gastrointestinal illness (AGI) caused by private well contamination in the county. Microbial source tracking was used to associate predicted cases of illness with bovine, human, or unknown fecal sources. RESULTS: Results suggest that private well contamination could be responsible for as many as 301 AGI cases per year in Kewaunee County, and that 230 and 12 cases per year were associated with a bovine and human fecal source, respectively. Furthermore, Cryptosporidium parvum was predicted to cause 190 cases per year, the most out of all 8 pathogens included in the QMRA. DISCUSSION: This study has important implications for land use and water resource management in Kewaunee County and informs the public health impacts of consuming drinking water produced in other similarly vulnerable hydrogeological settings.

“…Well selection produced a sample of wells that represented the five main aquifer types (sand and gravel, sandstone, crystalline rocks, carbonate rocks, and mixed rocks) and a range of geologic sensitivities of all public wells statewide. 21 , 22 …”

Section: Methodsmentioning

confidence: 99%

“…For example, Campylobacter jejuni was detected once but excluded because it was not quantified. 22 Rotavirus A was detected but excluded because the qPCR assay could not distinguish wild-type rotavirus from vaccine shed in stool, and Cryptosporidium andersoni was detected but excluded because no dose–response model exists for it. We did not estimate risk for pathogens that were not analyzed and/or detected, consistent with our emphasis on using site-specific hazard and exposure assessments.…”

Section: Methodsmentioning

confidence: 99%

Statewide Quantitative Microbial Risk Assessment for Waterborne Viruses, Bacteria, and Protozoa in Public Water Supply Wells in Minnesota

Burch

Rice

et al. 2022

Environ. Sci. Technol.

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Infection risk from waterborne pathogens can be estimated via quantitative microbial risk assessment (QMRA) and forms an important consideration in the management of public groundwater systems. However, few groundwater QMRAs use site-specific hazard identification and exposure assessment, so prevailing risks in these systems remain poorly defined. We estimated the infection risk for 9 waterborne pathogens based on a 2-year pathogen occurrence study in which 964 water samples were collected from 145 public wells throughout Minnesota, USA. Annual risk across all nine pathogens combined was 3.3 × 10 –1 (95% CI: 2.3 × 10 –1 to 4.2 × 10 –1 ), 3.9 × 10 –2 (2.3 × 10 –2 to 5.4 × 10 –2 ), and 1.2 × 10 –1 (2.6 × 10 –2 to 2.7 × 10 –1 ) infections person –1 year –1 for noncommunity, nondisinfecting community, and disinfecting community wells, respectively. Risk estimates exceeded the U.S. benchmark of 10 –4 infections person –1 year –1 in 59% of well-years, indicating that the risk was widespread. While the annual risk for all pathogens combined was relatively high, the average daily doses for individual pathogens were low, indicating that significant risk results from sporadic pathogen exposure. Cryptosporidium dominated annual risk, so improved identification of wells susceptible to Cryptosporidium contamination may be important for risk mitigation.