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Distinguishing possum and human faeces using faecol sterol analysis


The public has become increasingly aware of the potential hazards of faecally contaminated water. This heightened awareness is resulting in an increased frequency of water quality monitoring for the traditional microbial indicators, faecal coliforms, Escherichia coli and enterococci. There is also an expectation that when these indicators are detected, corrective action will be taken to eliminate these faecal indicators-and by inference the faecal pollution-from the water. While these traditional indicators are usually a good indication of microbial quality, and therefore the risk posed, they provide little guidance as to the source of the faecal pollution. Faecal coliforms and other traditional indicators are present in the faeces of humans, cows, sheep, dogs, ducks, seagulls and a wide range of other animals. Identifying the source of faecal pollution can be crucial for effective water management. A range of methods have been developed to identify sources of faecal contamination including PCR analysis of specific DNA fragments, culturing of alternative organisms, and detection of chemicals including fluorescent whitening agents (FWAs), caffeine, and faecal sterols1. One key step in the validation of each method is to evaluate the presence of each marker in different animal sources. In New Zealand efforts have primarily focussed on faecal outputs from the human population (4.5 million), dairy cows (5.3 million), beef cattle (4.4 million), sheep (32 million) and various populations of wildfowl2, 3.

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