Coherence among Different Microbial Source Tracking Markers in a Small Agricultural Stream with or without Livestock Exclusion Practices

Abstract

h Over 1,400 water samples were collected biweekly over 6 years from an intermittent stream protected and unprotected from pasturing cattle. The samples were monitored for host-specific Bacteroidales markers, Cryptosporidium species/genotypes, viruses and coliphages associated with humans or animals, and bacterial zoonotic pathogens. Ruminant Bacteroidales markers did not increase within the restricted cattle access reach of the stream, whereas the ruminant Bacteroidales marker increased significantly in the unrestricted cattle access reach. Human Bacteroidales markers significantly increased downstream of homes where septic issues were documented. Wildlife Bacteroidales markers were detected downstream of the cattle exclusion practice where stream and riparian habitat was protected, but detections decreased after the unrestricted pasture, where the stream and riparian zone was unprotected from livestock. Detection of a large number of human viruses was shown to increase downstream of homes, and similar trends were observed for the human Bacteroidales marker. There was considerable interplay among biomarkers with stream flow, season, and the cattle exclusion practices. There were no to very weak associations with Bacteroidales markers and bacterial, viral, and parasitic pathogens. Overall, discrete sample-by-sample coherence among the different microbial source tracking markers that expressed a similar microbial source was minimal, but spatial trends were physically meaningful in terms of land use (e.g., beneficial management practice) effects on sources of fecal pollution. Microbial source tracking (MST) can help reveal the sources of fecal contamination in water resources (1-5). There are a suite of MST tools that have been used in this capacity (6); some of these include the antimicrobial resistance patterns of target bacteria (7, 8), bacterial markers (9), such as Bacteroidales markers (2), host specificity associated with parasitic organisms like Cryptosporidium (10, 11), mitochondrial DNA methods (12, 13), and virus host specificity (14-16). There is potential for these tools to help identify how different land uses can impact the sources of fecal pollution in open-surface-water systems like agricultural watersheds, systems typically prone to variable inputs of human, livestock, and wildlife feces. While these tools have potential utility for such assessments, they are different in their limits of detection, source discrimination power, spatial and temporal stability, persistence in different environmental matrices, and what they express biophysically in water samples; and as such, results from one method may not necessarily be coherent with those of another method (5,17,18). Under some circumstances, however, coherency, or a lack of it, can reveal what biomarkers are appropriate for the use at hand, and MST coherence with the occurrence of other fecal indicator organisms and pathogens can be viewed as an important factor for helping to identify mitigation measures that will reduce public health risks (19)...

Waterborne Viruses and F-Specific Coliphages in Mixed-Use Watersheds: Microbial Associations, Host Specificities, and Affinities with Environmental/Land Use Factors

“…The lowest percentages of human F-RNA coliphage detection were found at site 22 and site 24. Site 22 was located immediately downstream of a protected stream channel/riparian zone that received primarily agricultural drainage but, interestingly, has been a site subjected to septic system leakage inputs (6,39,55). The lowest animal F-RNA coliphage detection was at site 22.…”

“…Hence, its potential as a virus indicator is promising. To our knowledge, the studies by Wilkes et al (4,39) are some of the first to report NoV GIII in an agriculture-dominated watershed setting.…”

“…AdV have a double-stranded DNA genome and display great diversity, with 7 species and 52 serotypes, where AdV types 40 and 41 are typically associated with gastroenteritis in children (38). Detection of AdV can be used for fecal source tracking in water, as human, porcine, bovine, and avian AdV are host specific (1,39). AdV infections in animals are either asymptomatic or associated with mild enteric or respiratory diseases (1).…”

Long-Term Monitoring of Waterborne Pathogens and Microbial Source Tracking Markers in Paired Agricultural Watersheds under Controlled and Conventional Tile Drainage Management

“…In watersheds, which are open systems, the efficacy of a beneficial management practice (BMP) on microbial water quality will potentially be masked by multiple sources of fecal pollution (23)(24)(25)(26)(27)(28). This was underscored in a study by Wilkes et al (24), whereby occurrences of source-specific Bacteroidales microbial source tracking markers shifted as a result of restricting livestock access to streams.…”

“…Additionally, norovirus GIII (a/w bovines) and Torque teno sus virus (a/w swine), hepatitis E virus, norovirus GII (a/w swine and human), and rotavirus were analyzed for detection. Samples were processed as described by Wilkes et al (24,31). In synchrony with the virus samples, samples were also collected for detection and quantification of F-specific RNA (F-RNA) and F-DNA coliphages as described by Wilkes et al (24), resulting in F-RNA coliphages of human origin and animal origin.…”