|CORSI, STEVE - Us Geological Survey (USGS)|
|CARVIN, REBECCA - Us Geological Survey (USGS)|
|BURCH, T. - Us Geological Survey (USGS)|
|LUTZ, MICHELLE - Us Geological Survey (USGS)|
|MCDERMOTT, C. - University Of Wisconsin|
|BUSSE, K. - University Of Wisconsin|
|KLEINHEINZ, GRET - University Of Wisconsin|
|ZHU, JUN - University Of Wisconsin|
Submitted to: Environmental Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/14/2015
Publication Date: 12/31/2015
Publication URL: http://handle.nal.usda.gov/10113/5363523
Citation: Corsi, S.R., Borchardt, M.A., Carvin, R.B., Burch, T., Spencer, S.K., Lutz, M.A., McDermott, C.M., Busse, K., Kleinheinz, G.T., Zhu, J. 2015. Human and bovine viruses and bacteria at three great lakes beaches: Environmental variable associations and health risk. Environmental Science and Technology. 50:987-995.
Interpretive Summary: People that swim in lakes and rivers impacted by wastewater from humans or livestock can be exposed to pathogens. Water quality guidelines for when a beach should be closed to avoid swimmer illnesses have been established. These guidelines rely on easily measured indicator bacteria that are present in wastewater. The indicators are not pathogenic; they only indicate the swimming water could be contaminated with wastewater. In this study, instead of relying on indicator bacteria, we measured human and cattle-related pathogens in the water at three beaches along the western shore of Lake Michigan, identified environmental factors that affect pathogen levels, and estimated the probability that swimmers could become ill. We found pathogens in almost all the water samples we collected from the three beaches. Among pathogen types unique to either humans or cattle, the majority we found were from human wastewater. Two pathogenic bacteria, Campylobacter jejuni and Salmonella, that come from both humans and cattle as well as other animals, were frequently detected in the beach water. Wave and current directions, water temperature, and the amount of cloud cover in the sky were the most important environmental factors for predicting pathogen concentrations. Taking into account how these environmental factors vary over the course of a swimming season, the length of time people swim at a beach, and how much water they swallow during swimming, we found that even though pathogens were present at the beaches, the risk of becoming ill after swimming was very low, less than 3 chances in 100,000. Our risk estimates are consistent with those studies that relied on indicator bacteria, suggesting the water quality guidelines are useful for preventing illnesses among swimmers.
Technical Abstract: Waterborne pathogens were detected in 96% of samples collected at three Lake Michigan beaches during the summer of 2010. Linear regression models were developed to explore environmental factors that may be influential for pathogen prevalence. Simulation of pathogen concentration using these models, direct pathogen sample results, and dose-response information for pathogens were used to estimate human health risk. Samples were collected and quantified for 22 pathogens in four microbial categories (human viruses, bovine viruses, protozoa and pathogenic bacteria). All three beaches had detections of human and bovine viruses and pathogenic bacteria indicating the influence of multiple contamination sources at these beaches. Among the three beaches, occurrence ranged from 40-87% for human viruses, 65-87% for pathogenic bacteria, and 13-35% for bovine viruses. Protozoa (Cryptosporidium parvum) were not detected during the study. Mean concentrations ranged from 7.3-364 gc/L for human viruses, from 163-3780 gc/L for pathogenic bacteria, and from 1.8-88.1 gc/L for bovine viruses. The most prevalent human viruses were enterovirus (47% occurrence) followed by adenovirus A (27% occurrence) and adenovirus C, D and F (14% occurrence). Of the pathogenic bacteria, Salmonella spp. and Campylobacter jejuni were detected most frequently (69% and 62% respectively). Bovine polyomavirus and bovine rotavirus A were detected most frequently among the four detected bovine viruses (14% and 10% respectively). Wave direction variables were influential in five regression models, cloud cover was an influential variable in four models, and currents and water temperature variables were influential in one model each. Quantitative Microbial Risk Assessment was done for the three most prevalent human pathogens (Campylobacter jejuni, Salmonella spp., and enteroviruses) to estimate risk of infection and illness and to investigate factors that most influence those estimates. Median infection risks for one-time swimming events during a swimming season were approximately 3×10-5, 7×10-9, and 6×10-7 for C. jejuni, Salmonella spp., and enteroviruses, respectively.