Fecal organisms

The excreta from warmblooded animals have countless micro-organisms, including bacteria, viruses, parasites, and fungi. Some of the organisms are pathogenic (disease causing), and many of the diseases carried by animals are transmittable to humans, and vice versa. Table 3-5 lists some of the diseases and parasites trans-mittable to humans from animal manure.

Many States use fecal coliform bacteria as an indicator of pollution from warmblooded animals, including man. The test for fecal coliforms is relatively simple and inexpensive compared to testing for specific pathogens. To test water for specific pathogens, such as salmonella, a number of samples of the suspect water must be collected to ensure that any pathogenic organisms in the water are actually captured.

The alternative to this impractical approach is to use an indicator organism that simply indicates when pollution from the waste of warmblooded animals is present, thus providing a way to estimate the potential for the presence of pathogenic organisms. The indicator organism must have the following characteristics:

• It must exist in large numbers in the source (animals, humans) in far greater numbers than the pathogens associated with the source.

Figure 3-5 Lake trophic states based on model by Vollenweider (adapted from EPA 1990)


Figure 3-5 Lake trophic states based on model by Vollenweider (adapted from EPA 1990)


Hydraulic residence time (years) Lake volume/outflow

• The die-off or regrowth rate of the indicator organism in the environment should be approximately the same as most pathogens.

• The indicator should be found only in association with the source of waste; its presence, therefore, would be a definite indicator that pollution from that type of source is present.

One indicator organism used widely to check for the presence of pathogens is a family of bacteria known as the coliforms. The total group of coliforms is associated with both the feces of warmblooded animals and with soils. However, the fecal coliform group represents a part of the total coliforms and is easily differentiated from the total coliforms during testing.

A positive test for fecal coliform bacteria is a clear indication that pollution from warmblooded animals exists. A high count indicates a greater probability that pathogenic organisms will be present.

Some fecal coliforms generally are in all natural water even without the influence of humans or their domestic animals. Birds, beaver, deer, and other wild animals contribute fecal coliforms to the water, either directly or in runoff. It is necessary, therefore, to have acceptable limits for fecal coliform bacteria, taking into account the beneficial use of the stream or water body. The EPA established water quality criteria for fecal coliform bacteria in its Quality Criteria for Water (1976), which many States have adopted. Typical limits are shown in table 3-6.

Some planners have used the ratio of fecal coliform (FC) to fecal streptococcus (FS) bacteria to help identify whether a suspected source of water pollution is from humans or other warmblooded animals. Table 3-7 shows the typical FC/FS ratios (as excreted) for different animal species.

Some questions remain regarding the usefulness of this method of identifying sources because the die-off rates between the two types of bacteria can differ

Table 3-5 Diseases and organisms spread by animal manure


Responsible organism


Responsible organism




Salmonella sp.

New Castle



Leptospiral pomona

Hog Cholera



Bacillus anthracis

Foot and Mouth



Mycobacterium tuberculosis



Mycobacterium avium

Johnes disease





Coccidoides immitus


Brucella abortus


Histoplasma capsulatum

Brucella melitensis


Various microsporum

Brucella suis

and trichophyton


Listeria monocytogenes



Clostridium tetani


Eimeria sp.


Pasturella tularensis


Balatidium coli.


Erysipelothrix rhusiopathiae


Toxoplasma sp.


E. coli (some serotypes)

Coliform mastitis-

E. coli (some serotypes)




Ascaris lumbricoides


Sarcocystis sp.


Q fever

Coxiella burneti

significantly. Consequently, it would only have meaning when the sampling point is close to the source. For this reason, the FC/FS ratio should be used with extreme caution as a tool for determining sources of pollution.

In more recent years, EPA has established criteria for using Escherichia coli (E. coli) and enterococci as a measure of harmful levels of bacterial pollution in ambient waters. E. coli (a fecal coliform type) and enterococci are natural inhabitants of warmblooded animals, and their presence in water samples is an indication of fecal pollution and the possible presence of pathogens. Some strains of enterococci are found outside warmblooded animals.

The EPA reports that a direct relationship between the density of enterococci and E. coli in water and the occurrence of swimming-associated gastroenteritis has been established through epidemiological studies of marine and freshwater bathing beaches. The resulting criteria can be used to establish recreational water standards. The EPA criteria for freshwater bathing are based on a statistically significant number of samples (generally not less than 5 samples equally spaced over a 30-day period). The geometric mean of the indicated bacterial densities should not exceed one or the other of the following:

E. coli 126 per 100 ml

Enterococci 33 per 100 ml

These criteria should not be used without also conducting a statistical analysis based on information provided by EPA.

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