Giardiasis is an illness caused by a parasite called Giardia intestinalis that causes diarrhoea and abdominal pain.

Giardia is found in the gut of humans and animals such as cattle, sheep, cats, dogs, rats and possums. It is passed on in the faeces (poo, tūtae) of infected animals and humans.

NOTE: Giardiasis is a notifiable disease - this means the local public health team may need to contact you and help trace the source of infection to reduce the risk to others of a large outbreak. Schedule of Notifiable Diseases, Ministry of Health 

image of giardia


  • 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 stream
  • the parasites can live in the environment for long periods, especially in lakes, rivers, streams and roof water
  • the risk of getting giardia is higher for travellers, people in childcare settings, and those who drink untreated water
  • giardia is common and widespread in many countries including New Zealand.


The main symptoms of giardia infection are:

  • diarrhoea (most common)
  • passing gas
  • greasy stools
  • stomach cramps
  • upset stomach or nausea
  • no symptoms (some people do not know they have giardia infection)

Most people have relatively mild disease and symptoms. Symptoms will usually appear 1-2 weeks after ingestion infected water or food and last two to six weeks in healthy adults.

In rarer cases, chronic illness can occur lasting months or even years.


For severe symptoms or persisting diarrhoea, a stool sample (poo) is needed to be collected and sent to the laboratory for testing.

  • Testing for giardia is indicated only when a person:
    • has diarrhoea for longer than 7 days
    • has recent attendance at a childcare centre
    • is immunocompromised 
    • has recently been overseas travel.
  • Until recently, 3 stool samples were required. Since most cases of giardia are found in the first sample, only 1 sample is now needed.


Antibiotic treatment is recommended for people who have tested positive for the organism, and symptomatic contacts.

40% of people develop a temporary milk intolerance after giardiasis so you may find it best to not consume milk and lactose-containing foods for approximately one month after treatment.


The best way to prevent giardia infection is to practice good hygiene, take care with preparing food, watch what you eat and wash your hands frequently and properly.

Take care about what water you drink and do not drink any water that may be contaminated.

When tramping or walking in parks, farms and national reserves, check if the streams or rivers are known to have any giardia.

Peel or wash fresh fruit and vegetables before eating.

Cover: all foods in the fridge, cupboard and outdoors. Separate and store raw and cooked foods so there is no chance of cross-contamination.

Follow the New Zealand Food Safety tips – the three Cs (clean, cook, chill) and the 20+20 rule (wash hands for 20 seconds and dry for 20 seconds).

  • Clean: food preparation areas, utensils, equipment and yourself.
  • Cook: raw foods well and leftovers until steaming hot. Ensure minced meat, chicken and sausages are cooked thoroughly.
  • Chill: store ready-to-eat foods between 0–4ºC. Any leftover cooked food should be covered and chilled (within two hours)

Learn more

Giardia infections  Centers for Disease Control and Prevention 

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