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Human Illnesses & Microbiology Detection Tests

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Published Date Written by Sharon Banks

Many South African citizens, especially those in poverty-stricken areas, still lack access to potable water and rely on untreated or poorly treated water resources e.g. rivers and boreholes. These wells may be/become contaminated thereby posing a significant health risk due to the danger of waterborne diseases and their complications, hence it is vitally important to monitor the microbial quality on a regular basis.

Some of the factors responsible for contamination are;
Typical Contamination (e.g. from pipe breaks and bursts, from repairs to network, infiltration or seepage from a contaminated source, sewage near groundwater sources, contamination from pit latrines/septic tanks, rubbish and faecal matter around standpipes) 
No disinfection (e.g. no chlorine dosing, no ozone dosing, no UV system)
No residual chlorine or low level of residual chlorine (e.g. chlorine not added at plant, residual chlorine below 0.2 mg/L at point of consumption)
Inadequate/post treatment contamination
Bacterial after growth in a distribution system.
Lack of maintenance (e.g. reservoirs and pipes not cleaned/flushed)
Poor design (e.g. long retention times in reservoir and distribution network, open reservoirs, large reticulation network with no additional chlorine dosing at reservoirs)
Sabotage/vandalism;
Water-borne diseases, which may be caused by bacterial, fungal, viral and parasitic pathogens, are responsible for debilitating effects on the users of untreated water. The major health risk associated with these drinking water sources is contamination by human or animal faeces.
Due to the complexity of the testing, time and cost, it is impractical to test water supply for all pathogens related to water-borne diseases. Hence general, non-specific, organism indicator tests are performed i.e. Heterotrophic plate counts, Total Coliforms, faecal coliforms, faecal enterococci (streptococci) and somatic coliphages.
The risks of being infected correlates with the level of water contamination and the amount of polluted water consumed. Higher concentrations will indicate a higher risk of contracting waterborne disease, even if small amounts of water are consumed. Thus bacteriological test results can be considered a direct indication of risk to health.
Water-borne diseases, which may be caused by bacterial, fungal, viral and parasitic pathogens, are responsible for debilitating effects on the users of untreated water. The major health risk associated with these drinking water sources is contamination by human or animal faeces.
Due to the complexity of the testing, time and cost, it is impractical to test water supply for all pathogens related to water-borne diseases. Hence general, non-specific, organism indicator tests are performed i.e. Heterotrophic plate counts, Total Coliforms, faecal coliforms, faecal enterococci (streptococci) and somatic coliphages.
The risks of being infected correlates with the level of water contamination and the amount of polluted water consumed. Higher concentrations will indicate a higher risk of contracting waterborne disease, even if small amounts of water are consumed. Thus bacteriological test results can be considered a direct indication of risk to health.
Escherichia coli (E.coli): is used as an indicator of faecal pollution by warm blooded animals (often interpreted as human faecal pollution). The presence of faecal pollution by warm blooded animals may indicate the presence of pathogens responsible for infectious disease such as gastroenteritis, cholera, dysentery and typhoid fever after ingestion of contaminated water.
Faecal Coliforms: are bacteria are found in water wherever the water is contaminated with faecal waste of human or animal origin. Faecal coliforms are primarily used to indicate the presence of bacterial pathogens such as Salmonella spp., Shigella spp., Vibrio cholerae, Campylobacter jejuni, Campylobacter coli, Yersinia enterocolitica and pathogenic E. coli. These organisms can be transmitted via the faecal/oral route by contaminated or poorly treated water and may cause diseases such as gastroenteritis, salmonellosis, dysentery, cholera and typhoid fever.
Heterotrophic Plate Count: detects a wide range of bacteria and is used to assess the general bacterial quality of water. Pollution can give rise to conditions conducive to bacterial growth leading to high heterotrophic plate counts.
Total coliform: Indicative of the general hygienic quality of water and are primarily used in the evaluation of the operational efficiency of water treatment processes, Test result includes bacteria of faecal origin and several other bacterial groups. It also indicates microbial growth in the distribution system or post-treatment contamination of drinking water. The total coliform group includes bacteria of faecal origin and indicates the possible presence of bacterial pathogens such as Salmonella spp., Shigella spp., Vibrio cholerae, pathogenic E. coli, etc. High total coliform counts may be responsible for diseases such as gastroenteritis, salmonellosis, dysentery, cholera and typhoid fever.
Somatic coliphages: are a diverse group of phages which infect E.coli and certain closely related bacteria. These phages occur in large numbers in sewage and therefore the presence of somatic coliphages indicates faecal pollution. Viruses are important contributory agents of waterborne disease and can cause illness such as gastroenteritis, hepatitis, poliomyelitis and respiratory illness.

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