Animal Waste, Water Quality and Human Health

Indicators, sanitary surveys and source attribution techniques 333host-specific Bacteroides is not well-understood, as they have not been cultured,although some information is available on their survival and persistence (Kreader1998, Walters & Field 2006, Okabe & Shimazu 2007) and on their host rangeand specificity (Bernard and Field 2000a, Gawler et al. 2007, Shanks et al.2010). Other characteristics are less well understood at present (e.g. typicalconcentrations in natural samples, movement through catchments, relationshipswith enteric viruses). However clear source tracking may be conceptually, theactual application of the techniques and data interpretation is stillunder development.Data interpretation must be approached with care and sampling strategies, inparticular, need to be robust and relevant to the question(s) at hand. The impactsof point sources can be readily monitored using culture-based FIOs; sourceattribution techniques are not always needed (though they can provide weight ofevidence). The use of ultraviolet (UV) disinfection can complicate detection ofhost-specific markers using methods such as PCR, as the microorganisms arekilled yet their DNA may persist (Bae & Wuertz 2009). However, sourcetracking may be applied to understanding specific issues in water quality, oftenproviding very useful information on diffuse sources of pollution. For example,it may be useful in explaining a decline in water quality following rainfallevents, which can impact on shellfish and bathing waters, where increases infaecal bacteria may originate from agricultural run-off or from raw sewagethrough a discharging sanitary or combined sewer overflow (CSO) (Stapletonet al. 2009). Although these associations are informative, correlating the resultsof source attributions studies to pathogen presence and/or human healthoutcomes would represent a more robust means of public health protection.9.4.3 Correlation of host-specific markers withFIOs and pathogensThere are conflicting study results regarding the correlation of host-specificmarkers to elevated levels of FIOs. For example, a field study by Vogel et al.(2007) reported an absence of coliphages during periods when highconcentrations of E. coli were noted. In contrast, another study found a positivecorrelation between coliphages and FIOs, and also between F-RNA coliphagesand human adenoviruses (Ogorzaly et al. 2009). One field study found a poorcorrelation of bacterial and viral markers of human sewage with FIOs; however,the human-associated markers correlated well with each other (McQuaig et al.2006). Multiple studies have reported detection of human-associatedBacteroidales molecular markers when FIOs are low or absent ((Bernhard &Field 2000a, Boehm et al. 2003, Bower et al. 2005); such findings can