Occurrence of waterborne pathogens and Escherichia coli at offshore drinking water intakes in lake Ontario

The efficacy of current treatment processes to remove, inactivate, or reduce environmental bloom-forming Escherichia coli

Escherichia coli is excreted in high numbers from the intestinal tract of humans, other mammals, and birds. Traditionally, it had been thought that E. coli could grow only within human or animal hosts and would perish in the environment. Therefore, the presence of E. coli in water has become universally accepted as a key water quality indicator of fecal pollution. However, recent research challenges the assumption that the presence of E. coli in water is always an indicator of fecal contamination, with some types of E. coli having evolved to survive and grow in aquatic environments. These strains can form blooms in water storages, resulting in high E. coli counts even without fecal contamination. Although these bloom-forming strains lack virulence genes and pose little threat to public health, their presence in treated water triggers the same response as fecal-derived E. coli. Yet, little is known about the effectiveness of treatment processes in removing or inactivating them. This study evaluated the effectiveness of current treatment processes to remove bloom-forming strains, in comparison to fecal-derived strains, with conventional coagulation-flocculation-sedimentation and filtration investigated. Second, the effectiveness of current disinfection processes-chlorination, chloramination, and ultraviolet (UV) light to disinfect bloom-forming strains in comparison to fecal-derived strains-was assessed. These experiments showed that the responses of bloom isolates were not significantly different from those of fecal E. coli strains. Therefore, commonly used water treatment and disinfection processes are effective to remove bloom-forming E. coli strains from water.IMPORTANCEThe presence of Escherichia coli in water has long been used globally as a key indicator of fecal pollution and for quantifying water safety. Traditionally, it was believed that E. coli could only thrive within hosts and would perish outside, making its presence in water indicative of fecal contamination. However, recent research has unveiled strains of E. coli capable of surviving and proliferating in aquatic environments, forming blooms even in the absence of fecal contamination. While these bloom-forming strains lack the genes to be pathogenic, their detection in source or drinking water triggers the same response as fecal-derived E. coli. Yet, little is known about the efficacy of treatment processes in removing them. This study evaluated the effectiveness of conventional treatment and disinfection processes in removing bloom-forming strains compared to fecal-derived strains. Results indicate that these commonly used processes are equally effective against both types of E. coli, reassuring that bloom-forming E. coli strains can be eliminated from water.

Occurrence of human pathogenic viruses in drinking water and in its sources: A review

Since many waterborne diseases are caused by human pathogenic viruses, virus monitoring of drinking water (DW) and DW sources is crucial for public health. Therefore, the aim of this review was to describe the occurrence of human pathogenic viruses in DW and DW sources; the occurrence of two viruses proposed as novel indicators of human faecal contamination (Pepper mild mottle virus and Tobacco mosaic virus) was also reported. This research was focused on articles that assessed viral occurrence using molecular methods in the surface water used for DW production (SW-D), groundwater used for DW production (GW-D), DW and bottled-DW (BW). A total of 1544 studies published in the last 10 years were analysed, and 79 were ultimately included. In considering the detection methods, filtration is the most common concentration technique, while quantitative polymerase chain reaction is the most common quantification technique. Regarding virus occurrence in SW-D, GW-D, and DW, high percentages of positive samples were reported for adenovirus, polyomavirus and Pepper mild mottle virus. Viral genomes were frequently detected in SW-D and rarely in GW-D, suggesting that GW-D may be a safe DW source. Viral genomes were also detected in DW, posing a possible threat to human health. The lowest percentages of positive samples were found in Europe, while the highest were found in Asia and South America. Only three articles assessed viral occurrence in BW. This review highlights the lack of method standardization and the need for legislation updates.

Detection of Cryptosporidium spp. and Giardia spp. in Environmental Water Samples: A Journey into the Past and New Perspectives

Among the major issues linked with producing safe water for consumption is the presence of the parasitic protozoa Cryptosporidium spp. and Giardia spp. Since they are both responsible for gastrointestinal illnesses that can be waterborne, their monitoring is crucial, especially in water sources feeding treatment plants. Although their discovery was made in the early 1900s and even before, it was only in 1999 that the U.S. Environmental Protection Agency (EPA) published a standardized protocol for the detection of these parasites, modified and named today the U.S. EPA 1623.1 Method. It involves the flow-through filtration of a large volume of the water of interest, the elution of the biological material retained on the filter, the purification of the (oo)cysts, and the detection by immunofluorescence of the target parasites. Since the 1990s, several molecular-biology-based techniques were also developed to detect Cryptosporidium and Giardia cells from environmental or clinical samples. The application of U.S. EPA 1623.1 as well as numerous biomolecular methods are reviewed in this article, and their advantages and disadvantages are discussed guiding the readers, such as graduate students, researchers, drinking water managers, epidemiologists, and public health specialists, through the ever-expanding number of techniques available in the literature for the detection of Cryptosporidium spp. and Giardia spp. in water.

Associations between extreme precipitation, drinking water, and protozoan acute gastrointestinal illnesses in four North American Great Lakes cities (2009-2014)

Climate change is already impacting the North American Great Lakes ecosystem and understanding the relationship between climate events and public health, such as waterborne acute gastrointestinal illnesses (AGIs), can help inform needed adaptive capacity for drinking water systems (DWSs). In this study, we assessed a harmonized binational dataset for the effects of extreme precipitation events (≥90th percentile) and preceding dry periods, source water turbidity, total coliforms, and protozoan AGIs - cryptosporidiosis and giardiasis - in the populations served by four DWSs that source surface water from Lake Ontario (Hamilton and Toronto, Ontario, Canada) and Lake Michigan (Green Bay and Milwaukee, Wisconsin, USA) from January 2009 through August 2014. We used distributed lag non-linear Poisson regression models adjusted for seasonality and found extreme precipitation weeks preceded by dry periods increased the relative risk of protozoan AGI after 1 and 3-5 weeks in three of the four cities, although only statistically significant in two. Our results suggest that the risk of protozoan AGI increases with extreme precipitation preceded by a dry period. As extreme precipitation patterns become more frequent with climate change, the ability to detect changes in water quality and effectively treat source water of varying quality is increasingly important for adaptive capacity and protection of public health.

Survivor microbial populations in post-chlorinated wastewater are strongly associated with untreated hospital sewage and include ceftazidime and meropenem resistant populations

Wastewater treatment plant (WWTP) effluent has been implicated in the spread of antibiotic resistant bacteria (ARB), including pathogens, as the WWTP environment contains multiple selective pressures that may increase mutation rates, pathogen survivability, and induce gene transfer between bacteria. In WWTPs receiving hospital sewage, this selective effect may be more pronounced due to increased concentrations of antibiotics, ARB, and clinical pathogens from hospital sewage. To determine the extent to which hospital sewage contributes to the microbial community of disinfected wastewater which is released into the environment, we used 16S rRNA sequencing of hospital sewage, WWTP influent, primary effluent, Post-Chlorinated Effluent, and receiving sediments in a combined sewage system to track changes in microbial community composition. We also sequenced the culturable survivor community resistant to β-lactam antibiotics within disinfected effluent. Using molecular source tracking, we found that the hospital sewage microbiome contributes an average of 11.49% of the microbial community in Post-Chlorinated Effluents, suggesting microorganisms identified within hospital sewage can survive or are enriched by the chlorination disinfection process. Additionally, we identified 28 potential pathogens to the species level, seven of which remained detectable in Post-Chlorinated Effluent and environmental sediments. When Post-Chlorinated Effluents were cultured on media containing β-lactam antibiotics ceftazidime and meropenem, a diverse antibiotic resistant survivor community was identified including potential human pathogens Bacillus cereus, Bacillus pumilus, and Chryseobacterium indologenes. Together, these results indicate that although wastewater treatment does significantly reduce pathogenic loads and ARBs, their continual presence in disinfected wastewater and receiving sediments suggests additional treatment and microbial tracking systems are needed to reduce human and animal health risks.

Molecular detection of opportunistic pathogens and insights into microbial diversity in private well water and premise plumbing

Private well water systems in rural areas that are improperly maintained will result in poor drinking water quality, loss of water supply, and pose human health risk. The purpose of this study was to investigate the occurrence of fecal indicator bacteria (FIB) and opportunistic pathogens in private well water in rural areas surrounding New Orleans, Louisiana. Our results confirmed the ubiquitous nature of Legionella (86.7%) and mycobacteria (68.1%) in private well water in the study area, with gene concentration ranged from 0.60 to 5.53 and 0.67 to 5.95 Log₁₀ of GC/100 mL, respectively. Naegleria fowleri target sequence was detected in 16.8% and Escherichia coli was detected in 43.4% of the water samples. Total coliform, as well as Legionella and mycobacteria genetic markers' concentrations were significantly reduced by 3-minute flushing. Next-generation sequencing (NGS) data indicated that the abundance of bacterial species was significantly increased in water collected in kitchens compared with samples from wells directly. This study provided integrated knowledge on the persistence of pathogenic organisms in private well water. Further study is needed to explore the presence of clinical species of those opportunistic pathogens in private well water systems to elucidate the health risk.

The Ecobiomics project: Advancing metagenomics assessment of soil health and freshwater quality in Canada

Transformative advances in metagenomics are providing an unprecedented ability to characterize the enormous diversity of microorganisms and invertebrates sustaining soil health and water quality. These advances are enabling a better recognition of the ecological linkages between soil and water, and the biodiversity exchanges between these two reservoirs. They are also providing new perspectives for understanding microorganisms and invertebrates as part of interacting communities (i.e. microbiomes and zoobiomes), and considering plants, animals, and humans as holobionts comprised of their own cells as well as diverse microorganisms and invertebrates often acquired from soil and water. The Government of Canada's Genomics Research and Development Initiative (GRDI) launched the Ecobiomics Project to coordinate metagenomics capacity building across federal departments, and to apply metagenomics to better characterize microbial and invertebrate biodiversity for advancing environmental assessment, monitoring, and remediation activities. The Project has adopted standard methods for soil, water, and invertebrate sampling, collection and provenance of metadata, and nucleic acid extraction. High-throughput sequencing is located at a centralized sequencing facility. A centralized Bioinformatics Platform was established to enable a novel government-wide approach to harmonize metagenomics data collection, storage and bioinformatics analyses. Sixteen research projects were initiated under Soil Microbiome, Aquatic Microbiome, and Invertebrate Zoobiome Themes. Genomic observatories were established at long-term environmental monitoring sites for providing more comprehensive biodiversity reference points to assess environmental change.

Assessing microbial risk through event-based pathogen loading and hydrodynamic modelling

The aim of this study was to assess the variability of microbial risk associated with drinking water under various contaminant loading conditions in a drinking water source. For this purpose, a probabilistic-deterministic approach was applied to estimate the loadings of Cryptosporidium, Giardia, and Escherichia coli (E. coli) from fecal contamination sources during both dry and wet weather conditions. The relative importance of loads originating from various fecal contamination sources was also determined by a probabilistic approach. This study demonstrates that water resource recovery facilities were the dominant source of Giardia, yet rivers were more important with regards to Cryptosporidium. Estimated loadings were used as input to a three-dimensional hydrodynamic model of Lake Ontario; the fate and transport of microbial organisms were simulated at the influent of a drinking water intake. Discharge-based hydrodynamic modelling results were compared to observed concentrations. Simulated probability distributions of concentrations at the intake were used as an input to a quantitative microbial risk assessment (QMRA) model such that the variability of microbial risk in the context of drinking water could be examined. Depending on wind and currents, higher levels of fecal contamination reached the intake during wet weather loading scenarios. Probability distribution functions of Cryptosporidium, Giardia and E. coli concentrations at the intake were significantly higher during wet weather conditions when compared to dry conditions (p < 0.05). For all contaminants studied, the QMRA model showed a higher risk during wet weather (over 1 order of magnitude) compared to dry weather conditions. When considering sewage by-pass scenarios, risks remained below 2.7 × 10^-7 person^-1 day^-1 for Giardia and E. coli O157:H7. Limited data were available for Cryptosporidium in by-pass effluents and the risk is unknown; hence it is critical to obtain reliable loading data for the riskiest scenarios, such as those associated with water resource recovery facility by-passes.

Precipitation effects on parasite, indicator bacteria, and wastewater micropollutant loads from a water resource recovery facility influent and effluent

The variability of fecal microorganisms and wastewater micropollutants (WWMPs) loads in relation to influent flow rates was evaluated for a water resource recovery facility (WRRF) in support of a vulnerability assessment of a drinking water source. Incomplete treatment and bypass discharges often occur following intense precipitation events that represent conditions that deviate from normal operation. Parasites, fecal indicator bacteria, and WWMPs concentrations and flow rate were measured at the WRRF influent and effluent during dry and wet weather periods. Influent concentrations were measured to characterize potential bypass concentrations that occur during wet weather. Maximum influent Giardia and C. perfringens loads and maximum effluent Escherichia coli and C. perfringens loads were observed during wet weather. Influent median loads of Cryptosporidium and Giardia were 6.8 log oocysts/day and 7.9 log cysts/day per 1,000 people. Effluent median loads were 3.9 log oocysts/day and 6.3 log cysts/day per 1,000 people. High loads of microbial contaminants can occur during WRRF bypasses following wet weather and increase with increasing flow rates; thus, short-term infrequent events such as bypasses should be considered in vulnerability assessments of drinking water sources in addition to the increased effluent loads during normal operation following wet weather.

Prevalence, levels and seasonal variations of human enteric viruses in six major rivers in Alberta, Canada

The prevalence and seasonal variation of 7 viruses in 6 major rivers in Alberta were assessed using a combination of qPCR, cell culture and integrated cell culture with qPCR (ICC-qPCR). Water samples were collected monthly from rivers at different sites upstream and downstream of major urban centers. Seven viruses including rotavirus, adenovirus, astrovirus, norovirus, sapovirus, JC virus and enterovirus, were detected in at least one of the water samples at each site using qPCR. Rotavirus was most common with concentration ranging from 2.3 to 4.5 log₁₀ genomic equivalent (GE) copies/L. Norovirus, sapovirus, astrovirus, adenoviruses and JC virus peaked during the winter (November to March). Viruses were most prevalent at the Bow River sampling site downstream of the City of Calgary, followed by the North Saskatchewan River site downstream of the City of Edmonton and the Red Deer River site downstream of the City of Red Deer. The detection rates and quantity of viruses had significant difference in the sampling sites between upstream and downstream of major urban centers (p < 0.001). 14% of the samples tested positive using viral culture indicating the presence of infectious viruses in river. Sequencing analysis identified human rotavirus in 75% of the samples collected from downstream versus 37% of the samples collected from upstream sites (p < 0.02). Multivariate binary regression showed that human activity in watersheds is a significant determinant of viruses in Alberta's Rivers. The discharge from wastewater treatment plants may be the possible sources of viral contamination. Seasonal coincidence of acute viral gastroenteritis outbreaks and monthly peak occurrence of enteric viruses in river water implies potential impact of waterborne viruses on human health.

Weather, environmental conditions, and waterborne Giardia and Cryptosporidium in Iqaluit, Nunavut

Indigenous communities in the Arctic often face unique drinking water quality challenges related to inadequate infrastructure and environmental contamination; however, limited research exists on waterborne parasites in these communities. This study examined Giardia and Cryptosporidium in untreated surface water used for drinking in Iqaluit, Canada. Water samples (n = 55) were collected weekly from June to September 2016 and tested for the presence of Giardia and Cryptosporidium using microscopy and polymerase chain reaction (PCR). Exact logistic regressions were used to examine associations between parasite presence and environmental exposure variables. Using microscopy, 20.0% of samples tested positive for Giardia (n = 11) and 1.8% of samples tested positive for Cryptosporidium (n = 1). Low water temperatures (1.1 to 6.7 °C) and low air temperatures (-0.1 to 4.5 °C) were significantly associated with an increased odds of parasite presence (p = 0.047, p = 0.041, respectively). These results suggest that surface water contamination with Giardia and Cryptosporidium may be lower in Iqaluit than in other Canadian regions; however, further research should examine the molecular characterization of waterborne parasites to evaluate the potential human health implications in Northern Canada.

Temporal variability of parasites, bacterial indicators, and wastewater micropollutants in a water resource recovery facility under various weather conditions

Wastewater discharges lead to the deterioration of receiving waters through treated effluents and by-passes, combined and sanitary sewer overflows, and cross-connections to storm sewers. The influence of weather conditions on fecal indicator bacteria, pathogens and wastewater micropollutants on raw and treated sewage concentrations has not been extensively characterized. However, such data are needed to understand the effects of by-pass discharges and incomplete treatment on receiving waters. A water resource recovery facility was monitored for pathogenic parasites (Cryptosporidium oocysts, Giardia cysts), fecal indicator bacteria (Escherichia coli, Clostridium perfringens), and wastewater micropollutants (caffeine, carbamazepine, 2-hydroxycarbamazepine, acesulfame, sucralose, and aspartame) during 6 events under different weather conditions (snowmelt and trace to 32 mm 2-day cumulative precipitation). Greater intra- and inter-event variability was observed for Giardia, E. coli and C. perfringens than for studied WWMPs. Even with the addition of inflow and infiltration, daily variations dominated concentration trends. Thus, afternoon and early evening were identified as critical times with regards to high concentrations and flows for potential by-pass discharges. Peak concentrations of Giardia were observed during the June wet weather event (1010 cysts/L), with the highest flowrates relative to the mean monthly flowrate. Overall, Giardia, E. coli and C. perfringens concentrations were positively correlated with flowrate (R > 0.32, p < 0.05). In raw sewage samples collected under high precipitation conditions, caffeine, carbamazepine and its metabolite 2-OH-carbamazepine were significantly correlated (p < 0.05) with Giardia, E. coli, and C. perfringens demonstrating that they are useful markers for untreated sewage discharges. Data from the study are needed for estimating peak concentrations discharged from wastewater sources in relation to precipitation or snowmelt events.

Sick leave due to diarrhea caused by contamination of drinking water supply with Cryptosporidium hominis in Sweden: a retrospective study

We investigated sick leave from work, studies, preschool, and kindergarten occurring between 1 November 2010 and 31 January 2011 and associated with a waterborne outbreak of diarrhea caused by Cryptosporidium hominis in late November 2010 in Östersund, Sweden with 45.2% of 60,000 residents being symptomatic. A questionnaire defining acute watery diarrhoea and/or ≥3 diarrhea episodes/day as cryptosporidiosis was sent to 1,508 residents in late January 2011 (response rate 69.2%). Among adults aged 18-60 years, 24.0% took sick leave for a mean of 4.6 (SD ± 4.0) days due to cryptosporidiosis, and an additional 10.6% were absent from work a mean of 4.0 (±2.2) days to care for symptomatic children. Among children (aged ≤17 years), 35.0% stayed home sick from kindergarten/preschool or school/university for a mean of 5.2 (±3.8) days resulting in 5.1 (±4.4) days of absence from work per sick child shared between parents/guardians. The estimated total number of sick leave days was 50,000 for adults and 20,700 for children, with an estimated direct cost of €7 million for employers. The potential impact on society of sick leave caused by waterborne diseases must be considered in decisions regarding the quality of drinking water.

Where Did They Come from-Multi-Drug Resistant Pathogenic Escherichia coli in a Cemetery Environment?

Human burial in cemeteries facilitates the decomposition of corpses without posing a public health danger. However, the role of cemeteries as potential environmental reservoirs of drug-resistant pathogens has not been studied. Thus, we investigated cemeteries as potential environmental reservoirs of multi-drug resistant (MDR) pathogenic Escherichia coli. E. coli isolates were obtained from water samples (collected from surface water bodies and boreholes in three cemeteries) after isolation using the Colilert^® 18 system. Pathogenic potentials of the isolates were investigated using real-time polymerase chain reactions targeting seven virulence genes (VGs) pertaining to six E. coli pathotypes. The resistance of isolates to eight antibiotics was tested using the Kirby–Bauer disc diffusion method. The mean E. coli concentrations varied from <1 most probable number (MPN)/100 mL to 2419.6 MPN/100 mL with 48% of 100 isolates being positive for at least one of the VGs tested. Furthermore, 87% of the isolates were resistant to at least one of the antibiotics tested, while 72% of the isolates displayed multi-drug resistance. Half of the MDR isolates harboured a VG. These results suggest that cemeteries are potential reservoirs of MDR pathogenic E. coli, originating from surrounding informal settlements, which could contaminate groundwater if the cemeteries are in areas with shallow aquifers.

Quantitative microbial risk assessment (QMRA) shows increased public health risk associated with exposure to river water under conditions of riverbed sediment resuspension

Although higher microbial concentrations have been reported in sediments than in the overlying water column, most quantitative microbial risk assessment (QMRA) studies have not clearly indicated the contribution of sediment-borne pathogens to estimated risks. Thus, the present study aimed at determining the public health risk associated with exposure to pathogenic bacteria in polluted river water under undisturbed conditions and conditions of sediment resuspension in the Apies River, Gauteng, South Africa. Microbial pathogens were isolated and identified using culture and molecular methods. The beta-Poisson dose-response model was used to estimate the probability of infection (Pi) with the various pathogens, following accidental/intentional ingestion of 1mL or 100mL (or 50mL) of untreated river water. Mean wet season Escherichia coli counts ranged between 5.8E+01 and 8.8E+04MPN/100mL (water column) and between 2.40E+03 and 1.28E+05MPN/100mL (sediments). Mean dry season E. coli counts ranged between 5.11E+00 and 3.40E+03MPN/100mL (water column) and between 5.09E+00 and 6.30E+03MPN/100mL (sediments). Overall (water and sediments) Vibrio cholerae was the most detected pathogen (58.8%) followed by Salmonella spp. (23.9%) and Shigella (10.1%). Ingestion of 1mL of river water could lead to 0%-4% and 1%-74% Pi with E. coli during the dry and wet season, respectively. During the dry season, the Pi with V. cholerae, Salmonella spp. and Shigella spp. were 0%-1.39%, 0%-4.11% and 0%-0.16% respectively, depending on volume of water ingested. The risks of infections with all microorganisms increased during the wet season. A 2-log increase in water E. coli count following sediments disturbance led to approximately 10 times higher Pi with E. coli than when sediments were undisturbed. Therefore, the use of the untreated water from the Apies River for drinking, household purposes or recreational activities poses a potential health risk to the users of the river.

Influencing factors and applicability of the viability EMA-qPCR for a detection and quantification of Campylobacter cells from water samples

In recent years, increasing numbers of human campylobacteriosis cases caused by contaminated water have been reported. As the culture-based detection of Campylobacter is time consuming and can yield false-negative results, the suitability of a quantitative real-time PCR method in combination with an ethidium monoazide pretreatment of samples (EMA-qPCR) for the rapid, quantitative detection of viable Campylobacter cells from water samples was investigated. EMA-qPCR has been shown to be a promising rapid method for the detection of viable Campylobacter spp. from food samples. Application of membrane filtration and centrifugation, two methods frequently used for the isolation of bacteria from water, revealed a mean loss of up to 1.08 log10 cells/ml from spiked samples. Both methods used alone lead to a loss of dead bacteria and accumulation of viable bacteria in the sample as shown by fluorescence microscopy. After filtration of samples, no significant differences could be detected in subsequent qPCR experiments with and without EMA pretreatment compared to culture-based enumeration. High correlations (R(2)= 0.942 without EMA, R(2) = 0.893 with EMA) were obtained. After centrifugation of samples, qPCR results overestimated Campylobacter counts, whereas results from both EMA-qPCR and the reference method were comparable. As up to 81.59% of nonviable cells were detected in pond water, EMA-qPCR failed to detect correct quantities of viable cells. However, analyses of spiked tap water samples revealed a high correlation (R(2) = 0.863) between results from EMA-qPCR and the reference method. After membrane filtration, EMA-qPCR was successfully applied to Campylobacter field isolates, and results indicated an advantage over qPCR by analysing defined mixtures of viable and nonviable cells. In conclusion, EMA-qPCR is a suitable method to detect viable Campylobacter from water samples, but the isolation technique and the type/quality of the water sample impact the results.

A national investigation of the prevalence and diversity of thermophilic Campylobacter species in agricultural watersheds in Canada

The occurrence and diversity of thermophilic Campylobacter species (C. jejuni, coli, and lari) were studied in water samples from four river basins located across Canada. These basins located in Quebec (Bras d'Henri), Alberta (Oldman), Ontario (South Nation), and British Columbia (Sumas) represented some of the most intensive farming areas in Canada for hog, beef cattle, dairy cattle, and poultry, respectively. This study analyzed 769 water samples collected from 23 monitoring sites with agricultural influence, and four reference sites with limited or no agricultural influence. Water samples were collected bi-weekly over two years and analyzed for Campylobacter using a semi-quantitative minimum probable number (MPN) enrichment protocol. Putative isolates were confirmed by genus- and species-specific multiplex polymerase chain reaction (PCR) assays. A total of 377 (49%) water samples were positive for campylobacters with 355 samples having a cell density ranging from 4 to 4000 MPN L(-1). Campylobacters were more common at agricultural than reference sites in each river basin, although this difference was not significant in the Oldman and South Nation (p > 0.05). Campylobacter was significantly more common in the Bras d'Henri and Sumas (63%) compared to the South Nation (45%) and Oldman (33%) River basins (p < 0.05). C. jejuni, C. coli and C. lari were detected in each river basin, and these species occurred in 45% (n = 168), 34% (n = 128) and 19% (n = 73), of all Campylobacter positive samples, respectively. The remaining Campylobacter positive water samples without these three species (n = 67; 18%) were identified as other Campylobacter species. C. jejuni was the predominant species occurring in the Sumas, Oldman and South Nation River basins. However, in the Bras d'Henri River basin with intensive hog production, C. coli was the predominant species. This study found campylobacters to be common in some agricultural systems with intensive livestock farming activities, and different river basins could have strikingly different profiles of either C. jejuni or C. coli as the predominant waterborne thermophilic Campylobacter species.