Potential Bacterial Pathogens In Feces Bacteria Disease Symptomless Carrier

Campylobacter Diarrhea yes

E. coli Diarrhea yes

Salmonella typhi Typhoid fever yes

Salmonella paratyphi Paratyphoid fever yes

Other Salmonellae Food poisoning yes

Shigella Dysentery yes

Vibrio cholerae Cholera yes

Other Vibrios Diarrhea yes

Yersinia Yersiniosis yes

Source: Feachem et al., 1980

million to one trillion viruses can be excreted with each gram of fecal material.15


Of the pathogenic bacteria, the genus Salmonella is significant because it contains species causing typhoid fever, paratyphoid, and gastrointestinal disturbances. Another genus of bacteria, Shigella, causes dysentery. Myobacteria cause tuberculosis (see Table 7.4). However, according to Gotaas, pathogenic bacteria "are unable to survive temperatures of550-60°Cfor longer than 30 minutes to one hour." 16

The pathogenic protozoa include Entamoeba histolytica (causing amoebic dysentery), and members of the Hartmanella-Naegleria group (causing meningo-encephalitis — see Table 7.5). The cyst stage in the life cycle of protozoa is the primary means of dissemination as the amoeba die quickly once outside the human body. Cysts must be kept moist in order to remain viable for any extended period.17

Finally, a number of parasitic worms pass their eggs in feces, including hookworms, roundworms (Ascaris) and whipworms (see Table 7.6). Various researchers have reported 59 to 80 worm eggs in sampled liters of sewage. This suggests that billions of pathogenic worm eggs may reach an average wastewater treatment plant daily. These eggs tend to be resistant to environmental conditions due to a thick outer covering,18 and they are extremely resistant to the sludge


Parasitic Worms

Table 7.5

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