Faecal indicators/pathogens

Origin of the Water-Borne Pathogens and Faecal Indicators Present... 

Rain and Densities of Faecal Pathogens and Indicators in Water Sources. 154... 

Only a small fraction of faecal contaminants contributed to the enviromnent through human and animal faeces reach new hosts to infect them. Many of the defecated microorganisms never reach the soil and/or water bodies, since faecal wastes are submitted to purification (water) and hygienization (solids) processes, which remove a fraction of the pathogens and indicators. An important fraction of those that reach either the soil or water are removed (adsorption to soil particles and suspended solids, followed by sedimentation) and/or inactivated by natural stressors (physical, chemical and biological) in soil and water bodies. 

Abundant literature on the increase of the densities of faecal pathogens and indicators in water sources during dry and rainy periods and the significant effect of rain in water-borne infectious disease outbreaks exist and prove all these assertions. 

First evidences of the impact of heavy rainfall on the epidemiology of enteric pathogens were obtained from studies on the presence of various faecal organisms, both pathogens and indicators in water. Increased numbers of pathogens and indicators in different water bodies, including drinking water, had been reported after heavy rains. 

Increased amounts of faecal-oral water-borne pathogens (virus, bacteria and protozoa) and microbial indicators (bacterial and viral) have been reported in groundwater bodies [18], karst springs [19, 20], surface freshwater [21-26], marine waters used for bathing [27-29] and shellfish growing [30] as well as tap water [31]. 

Pathogenic viruses, bacteria, protozoa and helminths may be present in raw municipal wastewater at the levels indicated in Table 11.3 and will survive in the environment for long periods. Pathogenic bacteria will be present in wastewater at much lower levels than that of the coliform group of bacteria, which are much easier to identify and enumerate (as total coliforms/100 ml). Escherichia coli are the most widely adopted indicator of faecal pollution and they can also be isolated and identified fairly simply, with their numbers usually being given in the form of faecal coliforms (FC)/100 ml of wastewater. 

A variety of physiological groups of bacteria are of importance for water quaUty. They participate in various natural processes in water. In addition, other bacteria are introduced from the environment, indicating general and faecal pollution. They include conditionally pathogenic and pathogenic bacteria. 

Thus, it has been shown that it is inadequate to relate pathogen occurrence in water to faecal contamination by traditional indicators [16]. 

E. coli is very rarely found in water when faecal pollution is absent, and testing for E. coli and coliforms is the most sensitive method of demonstrating faecal pollution. Confirmation of the presence of E. coli indicates faecal pollution and the possible presence of intestinal pathogens. High counts suggest recent or heavy pollution, whilst low counts suggest slight pollution or pollution at some time in the distant past. 

Indeed, symptoms of pathogen-specific enteritis are not sufficiently unusual to distinguish a disorder form those due to Salmonella, Shigella, Campylobacter or Yersinia or other pathogens. The combination of fever and faecal leukocytes or erythrocytes is indicative of inflammatory diarrhoea,but the definite diagnosis is based on culture or demonstration of specific organisms on stained faecal smears. 

Escherichia coli normally lives in intestinal tracts and, in particular, in the large intestine of human beings and warm-blooded animals. Outside the intestinal tract, it can only live for a short time in water and in the ground and therefore indicates relatively fresh faecal contamination. Thus, when Escherichia coli is present in water, one also has to reckon on the presence of pathogenic intestinal bacteria such as Salmonella, Shigella and cholera vibrios. Escherichia coli is easy to cultivate on culture mediums and can, by reason of its metabolic characteristics in the so-called... 

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