Healthy urine on its way out of the human body may contain up to 1,000 bacteria, of several types, per milliliter. More than 100,000 bacteria of a single type per milliliter signals a urinary tract infection. Infected individuals will pass pathogens in the urine that may include:
Salmonella typhi Typhoid
Salmonella paratyphi Paratyphoid fever
Escherichia coli Diarrhea
Schistosoma haematobium schistosomiasis
Source: Feachem et al., 1980; and Franceys, et al. 1992; and Lewis, Ricki. (1992). FDA Consumer, September 1992. p. 41.
MINIMAL INFECTIVE DOSES For Some Pathogens and Parasites
Pathogen Minimal Infective Dose
Ascaris 1-10 eggs
Cryptosporidium 10 cysts
Entamoeba coli 10 cysts
Escherichia coli 1,000,000-100,000,000
Giardia lamblia 10-100 cysts
Hepatitis A virus 1-10 PFU
Salmonella spp 10,000-10,000,000
Shigella spp 10-100
Streptococcus fecalis 10,000,000,000
Vibrio cholerae 1,000
Pathogens have various degrees of virulence, which is their potential for causing disease in humans. The minimal infective dose is the number of organisms needed to establish infection.
Source: Bitton, Gabriel. (1994). Wastewater Microbiology. New York: Wiley-Liss, Inc., p. 77-78. and Biocycle, September 1998, p. 62.
ary habits. It should be understood that the breath one exhales can also be the carrier of dangerous pathogens, as can one's saliva and sputum. The issue is confused by the notion that if something is potentially dangerous, then it is always dangerous, which is not true. Furthermore, it is generally not understood that the carefully managed thermophilic composting of humanure converts it into a sanitized agricultural resource. No other system of fecal material and urine recycling or disposal can achieve this without the use of dangerous chemical poisons or a high level of technology and energy consumption.
Even urine, usually considered sterile, can contain disease germs (see Table 7.1). Urine, like humanure, is valuable for its soil nutrients. It is estimated that one person's annual urine output contains enough soil nutrients to grow grain to feed that person for a year.13 Therefore, it is just as important to recycle urine as it is to recycle humanure, and composting provides an excellent means for doing so.
The pathogens that can exist in humanure can be divided into four general categories: viruses, bacteria, protozoa and worms (helminths).
First discovered in the 1890s by a Russian scientist, viruses are among the simplest and smallest of life forms. Many scientists don't even consider them to be organisms. They are much smaller and simpler than bacteria (some viruses are even parasitic to bacteria), and the simplest form may consist only of an RNA molecule. By definition, a virus is an entity which contains the information necessary for its own replication, but does not possess the physical elements for such replication — they have the software, but not the hardware. In order to reproduce, therefore, viruses rely on the hardware of the infected host cell which is re-programmed by the virus in order to reproduce viral nucleic acid. As such, viruses cannot reproduce outside the host cell.14
There are more than 140 types of viruses worldwide that can be passed through human feces, including polioviruses, coxsack-ieviruses (causing meningitis and myocarditis), echoviruses (causing meningitis and enteritis), reovirus (causing enteritis), adenovirus (causing respiratory illness), infectious hepatitis (causing jaundice), and others (see Table 7.3). During periods of infection, one hundred
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