Animal Waste, Water Quality and Human Health

Indicators, sanitary surveys and source attribution techniques 331An ideal source attribution technique would be as easy and inexpensive asmonitoring for FIOs, rapidly providing reliable, quantitative andeasy-to-interpret differential diagnoses of faecal sources. The results of an idealmethod should reflect the probability of the presence of human pathogens. Inorder for faecal source tracking methods to meet these criteria, the followingshould ideally be met (US EPA 2005, Harwood et al. 2007):• each identifiable host source must possess unique characteristics thatunequivocally distinguish it from other related or non-related sources(host-specific marker);• the even distribution of host-specific markers must be predictable amonghosts and have a similar environmental survival profile as host-specificmarkers from other species;• the identifying trait (host-specific marker) must be detectable in water atvarying concentrations;• the host-specific traits should have a similar distribution and environmentalsurvival profile as the FIO used to monitor that water body; and,• the host-specific markers should correlate well with pathogen presence, fateand transport in the aquatic environment.9.4.2 Limitations and challenges of faecal sourcetracking methodsFaecal source tracking, or MST, refers to the assignation of a pollutant source bytracing (fate and transport) or identifying a variety of microorganisms and/orchemicals back to their host (faecal source). Microbial source tracking mayemploy typical water quality indicators such as E. coli and enterococci as wellas secondary or alternative indicators as previously described (Table 9.1).Analytical methods vary widely and may include DNA “fingerprinting”, whichrefers to the analysis of patterns generated from the DNA of the organism andare generally performed on cultured isolates. DNA fingerprinting of faecalcoliforms, E. coli and faecal streptococci (enterococci) forms a subset of MST,one tool in a toolbox of potential methods (USEPA 2005). Other MST methodsthat do not require culturing are also discussed below.A variety of faecal bacteria, including traditional FIOs and other microbes,may lend themselves well to source attribution techniques and are the subjectof an extensive body of recently published literature. In order to estimaterelative contributions to a waterbody from an array of possible faecal sources,host-specific markers should have a distribution within their host andenvironmental survival profiles that mimic those of pathogens (USEPA 2005,