HF183. The HF183 marker is the recommended starting point for detecting human
fecal material because it provides the best combination of sensitivity and specificity. Although it was ranked as the best on sensitivity among the human markers
tested, it has been shown to occasionally detect (“cross-react”) both chicken and
dog feces. If those sources pose a concern in the watershed under investigation, or if
managers simply desire to add certainty about the results, HF183 can be paired with
HumM2.
A different approach that is worth considering is adding human virus measurements to validate bacterial marker results [76]. If cross-reactivity has occurred with
the human bacterial markers or if the cost of mitigation is high, as is typical in urban
coastal cities, the costs might justify additional verification for the presence of
human fecal material, especially municipal sewage. Human viruses have a very
high specificity to human waste and almost no cross-reactivity with other fecal
sources. Of the many fecal viruses that exist, markers for DNA viruses such as
human adenovirus [67, 68] and human polyomavirus [68] are among the more
sensitive and robust. These viruses are fairly widespread among humans and a
sizable portion of the population sheds polyomaviruses passively. However, the
low-density occurrence of viruses in water and the difficulty of concentrating them
efficiently with the current technology provide barriers to routinely use viral
markers. Detection may be enhanced by collecting and concentrating large volumes
of water samples, up to 1,000 times more water than the typical 100 mL sample
needed for bacterial source markers. Such large sample volumes add logistical
challenges and expense as the sample must be processed on-site or transported to
the laboratory in large volumes. Due to the specialized steps required in virus
concentration and recovery, partnering with an experienced research laboratory is
mandatory if virus detection is used as part of an ongoing MST effort [6, 76, 77].
3.5 Non-human-Source Markers
The SIPP study identified markers that sufficiently meet the design performance
criteria and are recommended for source identification from birds, dogs, horses,
cattle/ruminants, and pigs.
At present, four bird markers (Gull2SYBR, LeeSeaGull, Gull2Taqman,
Gull2Endp) from several sea bird-associated assays have been evaluated and
published [78, 79]. Of these four markers, the Gull2SYBR [70] and the LeeSeaGull
[71] markers were considered best for routine use because these markers consistently displayed sensitivity and specificity across participating laboratories. All four
bird markers detected gull and sometimes goose and pigeon feces. Also, the
distribution of the bird marker bacterium (Catellicoccus marimammalium) among
all the various species of shorebirds is not known. Therefore, the Gull2SYBR and
LeeSeaGull markers should be considered general “bird” assays and not necessarily
specific to gulls. Several new bird-associated MST assays for gulls, Canada geese,
ducks, and chickens were reported too late for inclusion in the SIPP study, but may
Microbial Source Tracking: Advances in Research and a Guide to Application
275
fecal material because it provides the best combination of sensitivity and specificity. Although it was ranked as the best on sensitivity among the human markers
tested, it has been shown to occasionally detect (“cross-react”) both chicken and
dog feces. If those sources pose a concern in the watershed under investigation, or if
managers simply desire to add certainty about the results, HF183 can be paired with
HumM2.
A different approach that is worth considering is adding human virus measurements to validate bacterial marker results [76]. If cross-reactivity has occurred with
the human bacterial markers or if the cost of mitigation is high, as is typical in urban
coastal cities, the costs might justify additional verification for the presence of
human fecal material, especially municipal sewage. Human viruses have a very
high specificity to human waste and almost no cross-reactivity with other fecal
sources. Of the many fecal viruses that exist, markers for DNA viruses such as
human adenovirus [67, 68] and human polyomavirus [68] are among the more
sensitive and robust. These viruses are fairly widespread among humans and a
sizable portion of the population sheds polyomaviruses passively. However, the
low-density occurrence of viruses in water and the difficulty of concentrating them
efficiently with the current technology provide barriers to routinely use viral
markers. Detection may be enhanced by collecting and concentrating large volumes
of water samples, up to 1,000 times more water than the typical 100 mL sample
needed for bacterial source markers. Such large sample volumes add logistical
challenges and expense as the sample must be processed on-site or transported to
the laboratory in large volumes. Due to the specialized steps required in virus
concentration and recovery, partnering with an experienced research laboratory is
mandatory if virus detection is used as part of an ongoing MST effort [6, 76, 77].
3.5 Non-human-Source Markers
The SIPP study identified markers that sufficiently meet the design performance
criteria and are recommended for source identification from birds, dogs, horses,
cattle/ruminants, and pigs.
At present, four bird markers (Gull2SYBR, LeeSeaGull, Gull2Taqman,
Gull2Endp) from several sea bird-associated assays have been evaluated and
published [78, 79]. Of these four markers, the Gull2SYBR [70] and the LeeSeaGull
[71] markers were considered best for routine use because these markers consistently displayed sensitivity and specificity across participating laboratories. All four
bird markers detected gull and sometimes goose and pigeon feces. Also, the
distribution of the bird marker bacterium (Catellicoccus marimammalium) among
all the various species of shorebirds is not known. Therefore, the Gull2SYBR and
LeeSeaGull markers should be considered general “bird” assays and not necessarily
specific to gulls. Several new bird-associated MST assays for gulls, Canada geese,
ducks, and chickens were reported too late for inclusion in the SIPP study, but may
Microbial Source Tracking: Advances in Research and a Guide to Application
275