Giardia is a food- and water-borne disease that is caused by a parasite found in the gut of infected humans and animals (eg, cattle, sheep, cats, dogs, rats and possums). Giardia is one of the most common diseases worldwide that is carried by water.


Giardia is passed on in the faeces (poos) of infected humans and animals. People become infected when they swallow the parasites.

Giardia is common in New Zealand. The parasites can live in the environment for long periods – especially in lakes, rivers, streams and roof water.

How do you get giardia?

You get giardia from:

  • drinking contaminated water or eating contaminated food
  • being in contact with infected animals that are carrying the parasite
  • being in close contact with someone who has giardia – eg, people living in the same house or if you’re looking after someone who has giardia
  • swallowing water that contains the giardia parasite while you’re swimming or playing in lakes, rivers, springs, ponds or streams.

Time off from kura or school

Children should stay away from kura or school until at least 48 hours after the diarrhoea has stopped.


The most common symptoms of giardiasis are diarrhoea, stomach cramps, bloating, nausea, loose and pale greasy stools, fatigue, and if symptoms persist, weight loss.

Some people have no symptoms, however they can still pass the disease to others.

The first signs of illness can appear from 3 to over 25 days after a person becomes infected. 

The infection can last for months if untreated.


Most people with giardia will get better without treatment.  It is important for people with diarrhoea to drink plenty of fluids to avoid dehydration. Some people may need prescription drugs, such as metronidazole and tinidazole, that are used to treat giardia.

Call Healthline 0800 611 116 if you are unsure what you should do.


You can avoid catching giardia by doing the following. 

  • Always wash hands thoroughly after going to the toilet, handling animals, changing nappies, and before preparing food and drinks.
  • Do not drink untreated water from rivers or lakes. Boiling water from these sources will kill giardia and other parasites. Some water filters may also remove these parasites. 
  • Avoid drinking unboiled tap water and eating uncooked foods when travelling in countries where the water supply may be unsafe.
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