What is E.coli?

Escherisha coli is a gram negative, rod shaped bacterium. It can survive with and without the presence of oxygen and is commonly found in the lower intestine of warm blooded animals.

Some strains of E.coli, you may have heard of E.coli 0157 are capable of causing severe illness, others do not.

Where is E.coli Found?

Unfortunately for us, water is a great conduit of E.coli, it can both survive and breed in water supplies. That means that bores, streams, rivers, springs and water tanks are all ideal habitats.

Most town supplies are treated and should be free of E.coli. However, if you are on small water supply or irrigation scheme, do not take this for granted.

Why is E.coli important?

E.coli is used as an indicator organism. If present it essentially proves that the water has been in contact with faeces and is therefore not safe. Many animals carry other disease-causing organisms that can make us sick. Testing for E.coli is a cost-effective screen that shows a high risk of pathogens being present in the supply.

How does E.coli get into my water supply?

We are not the only animals to inhabit the earth, or the only animals to need to drink water. Rainwater is almost always contamination as bird, possums, rats, mice and other animals often defecate on the roof, this washes into the tank when it rains.

Surface Water Sources like streams, rivers, and springs are used by animals to swim, wash and drink.

Bores, especially the which are shallow can become contaminated as water containing these organisms seeps down into the water table, though they can also be contaminated by flooding.

What other Pathogenic bacteria can be found in water?


Campylobacter is the name on everyone’s lips after the Havelock North Outbreak. This causes severe diarrhoea and sickness and in rare cases, long term complications.

In New Zealand, common waterborne pathogenic bacteria include:
  • Legionella
  • Salmonella - Causes diarrhea, fever, abdominal cramps
  • Shigella - Causes diarrhea, fever, abdominal cramps
  • Yersinia - Causes diarrhea, fever, abdominal pain, can mimic appendicitis

How can I test for E.coli and other bacteria?

An E.coli test is readily available

This should be used to indicate whether or not that water has been contaminated with faeces. If it has, it is best to assume that the water can make you sick and protect yourself accordingly.

Remember: Bacteria have no taste or smell, so the best protection is to make sure any water that you put near your mouth has been disinfected. Otherwise, the only indication of a problem that you will have is you or your family/friends getting sick.

How will I know what bacteria have made me sick?

Often a doctor won’t be able to tell you, these illnesses are often generically referred to as ‘gastroenteritis’ or ‘food poisoning’ (this can be a misnomer). However, if your symptoms are severe, you may be asked for a stool sample which can be tested.