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 passed on in the faeces 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, streams and so on.

Related websites

Ministry for Primary Industries
Information on safe food handling and preparation.

Better Health Channel
Victoria State Government (Australia) website. Provides health and medical information.

Centers for Disease Control and Prevention
Part of the United States Government’s Department of Health and Human Services. Deals with public health concerns.


If you have giardia, you could have:

  • foul smelling diarrhoea
  • stomach cramps and abdominal pain
  • nausea and vomiting
  • weight loss
  • bloating
  • slight fever
  • loss of appetite
  • headache
  • fatigue.

Your symptoms will appear between 3–25 days after you become infected. You can be ill for 3–4 days, then feel better, then the symptoms may come back.

If you don’t get treatment, this can continue and you can be infectious for months.


If you think you may have giardia, this is what you should do:

  • Go to your doctor. Take a specimen of some of your faeces (‘poos’) with you in a clean jar, as you’ll need a laboratory test.
  • If you do have giardia, your doctor will prescribe a medicine such as Flagyl or Dyzole.
  • While the diarrhoea lasts, drink plenty of water to prevent dehydration. Filtered water or water that has been boiled for one minute is safest.
  • If you have a child that is ill and they're not drinking, go back to your doctor.

Giardia is a notifiable disease. People with giardia should stay away from school, early childhood centres or work until well and for 48 hours after the last episode of diarrhoea or vomiting.


Here's what you can do to avoid getting giardia – or passing it on.


  • Avoid drinking water that may be contaminated – don’t drink untreated water from lakes, rivers or streams, or from an area where the water is unsafe because of poor sanitation or where there are no water treatment systems.
  • If you have to drink water that is taken from a roof, river or lake (eg, in a rural area), it should be boiled for 1 minute or put through an approved filter. The water filter should meet the standard AS/NZS4348:1995.


  • When swimming in swimming pools, hot pools or spa pools, take care to not swallow the water.
  • Don’t go swimming in a pool if you have diarrhoea. You need to wait at least 2 weeks after the symptoms have gone – and wash your hands before going for a swim.

Food preparation

  • To stop giardia spreading, wash your hands before and after preparing food, after playing or working with animals, and after going to the toilet or changing a baby’s nappy. You need to wash your hands thoroughly with soap and hot water, rinse well and dry them on a clean towel.

Tramping and camping

  • Use toilets, when they’re provided.
  • If there are no toilets, bury your toilet waste and paper at least 50 metres away from water sources, such as rivers and lakes.
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