E. Coli: What is it and what are the health effects?

Aidan Holland

Tuesday, 5th March 2019
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E. Coli VTEC drinking water test

E Coli are bacteria naturally present in the faeces of humans and animals. They live in large numbers on the walls of the intestine and their detection may indicate the presence of other more harmful bacteria, viruses and parasites that can cause serious illness.

Verocytotoxigenic Escherichia coli (VTEC) is a particular group of the bacterium E Coli. Although most strains of E Coli are harmless and live in the intestines of healthy humans and animals, VTEC strains produce a powerful toxin and can cause severe illnesses including gastroenteritis, dysentery, diarrhoea and a cholera-like syndrome. Enterohaemorrhagic E. coli  including the O157 strain found in national water supplies in recent years – can cause illnesses ranging from mild diarrhoea to haemorrhagic colitis. Individuals who are immuno-compromised such as the elderly, cancer patients and infants are at a particular risk from E. Coli contamination.

E Coli bacteria are commonly detected in groundwater supplies and there are a number possible reasons for contamination. From experience, our laboratories generally find that the natural filtration processes around the wells are inadequate. Where soil cover may be thin and the ground around the well contains fractured rock or karst features, E Coli from sources such as septic tanks, burst sewage pipes or agricultural run-off can make their way into the drinking water supply. To mitigate this risk, Environment and Health agencies advise that wells should be protected with a well cap and concrete casing and be tested annually for microbiological contamination.

E. Coli are also found in abundance in surface waters such as rivers and lakes. This is particularly true of areas where animals are standing in water along the catchment and where there may be poor land-spreading or farmyard management practices, or where wastewater treatment facilities are inadequate (e.g. defective septic tanks/municipal wastewater treatment systems).

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