Animal Waste, Water Quality and Human Health

Indicators, sanitary surveys and source attribution techniques 329Source attribution includes several methods which may have the ability todetermine whether faecal pollution is from human or non-human sources.Source tracking methods have successfully been applied to identify non-pointsource pollution responsible for the faecal contamination of water systems(reviewed in USEPA 2005). Methods for source attribution can be separatedinto three groups: molecular, biochemical and chemical. Many of the molecularand biochemical techniques have been applied or suggested for use in watershedstudies and have been summarized (Simpson et al. 2002, Meays et al. 2004,Field & Samadpour 2007, Sadowsky & Santo Domingo 2007, Santo Domingoet al. 2007, Stoeckel & Harwood 2007, Yan & Sadowsky 2007). One of theseapproaches focuses on detecting host-specific molecular markers using the16SrDNA gene of Bacteroides and the larger taxon, the Bacteriodales (Allsop& Sticker 1985, Fiksdal et al. 1985, Bernhard & Field, 2000a, 2000b, Dicket al. 2005). Bacteroidales constitutes one of the most numerous members of thehuman colonic flora. Known representatives are restricted to the gastrointestinaltract of warm-blooded animals and, unlike coliforms, this taxon makes up asignificant portion of faecal bacteria (Finegold et al. 1983, Sghir et al. 2000),comprising approximately 30 percent of the flora in the human gut (Sears 2005).The application of this method has been used to detect and differentiate humanand ruminant sources of faecal pollution in the environment (Bernhard et al.2001, Lee et al. 2008, Reischer et al. 2008, Shanks et al. 2010).In addition to distinguishing between human and ruminant sources, DNAmarkers may also be employed to distinguish avian from human sources. In theupper mid-western United States, one library-independent study (see section 9.4.2below) used pooled genomic tester and driver DNAs in suppression subtractivehybridizations to enrich for host source-specific DNA markers for Escherichiacoli, originating from locally isolated geese (Hamilton et al. 2006). Whilesuccessful, this study results were applicable only to regional sources.Library-dependent MST efforts are also subject to regionalization for the bestresults (Stoeckel & Harwood 2007). A combination of both library-independentand library-dependent techniques may be necessary to provide the temporal andspatial acuity necessary to determine pollution sources (Edge et al. 2010).9.4.1 Chemical analysis (source tracking/water qualityindicators)In addition to MST techniques, chemical parameters have been used to identifyfaecal sources (reviewed in Scott et al. 2002, Meays et al. 2004, Hagedorn &Weisberg 2009). Caffeine and coprostanol are two markers which can be usedto confirm the presence of human sewage contaminated water. Caffeine is