Health conditions

Giardia infection (giardiasis)

What is giardia infection?

Giardiasis is a bowel (gut) infection caused by a parasite called Giardia lamblia, also known as Giardia intestinalis. The parasite attaches itself in large numbers to the wall of your bowel and interferes with your body’s natural absorption of nutrients.

In Western Australia, more than 700 cases of Giardia infection are reported each year.  More than half of all cases are in infants and children under 5. However, Giardia can infect anybody at any age.

How do you get giardia infection?

You can get Giardia infection (giardiasis) by putting anything in your mouth that has been directly or indirectly contaminated with animal or human faeces (poo) that contain Giardia.

Infection most often occurs by:

  • Swallowing polluted water from rivers, streams, springs, ponds, lakes, swimming pools, spas or ocean water
  • Eating uncooked food, fruit or vegetables that have been contaminated or have been washed with contaminated water
  • Touching your mouth after handling clothing, bedding, toilets, taps, toys and nappy changing tables used by an already infected person
  • Coming into contact with animals or soils that contain animal faeces
  • Exposure to faeces through sexual contact.
Although it is less common, food handlers can contaminate cooked food with Giardia if they do not wash their hands after going to the toilet.

Who is most likely to get it?

Some people are more likely to get Giardia infection, including:

  • children who are not toilet trained
  • childcare workers
  • international travellers, particularly to or from south-east Asia
  • hikers and campers.

Signs and symptoms

The following symptoms usually appear between 7 and 10 days after infection:

  • foul smelling greasy or watery diarrhoea
  • abdominal (stomach) cramps
  • nausea
  • fatigue
  • bloating
  • loss of appetite.

How do I know if I have been infected with Giardia?

Diagnosis must be made by a medical professional.

It is possible to be a carrier and spread the disease without being ill.


Consult your doctor for treatment, as prescription medications such as antibiotics are usually required. Chronic infection can last for months to years if left undiagnosed and untreated.

Avoid anti-vomiting or anti-diarrhoeal medications unless a doctor has prescribed or recommended them for you.

While you have the infection

  • Drink plenty of fluids such as plain water or oral rehydration drinks (available from your pharmacy).
  • Do not go to work until at least 24 hours after symptoms have stopped.
  • Do not handle or prepare food until at least 24 hours after symptoms have stopped.
  • Keep children home from school until at least 24 hours after symptoms have stopped.
  • People in hospitals, nursing homes and other residential facilities should be nursed in their own room, with a private bathroom until at least 24 hours after symptoms have stopped.
  • Immediately remove and wash any clothes or bedding contaminated with vomit or diarrhoea using soap and hot water.
  • Thoroughly clean and disinfect contaminated surfaces with a bleach-based household cleaner immediately after any episode of vomiting.
  • Health care workers, child care workers and food handling workers should not attend work until 48 hours after symptoms have stopped.
  • Food handlers must have a medical clearance certificate before resuming food handling activities

How can giardiasis be prevented?

To stop the spread of infection:

  • Wash hands with soap and water after changing nappies and before preparing or handling food or drinks. To wash your hands effectively, lather thoroughly with soap and running water for at least 15 seconds. Dry your hands with a clean single use towel (e.g. paper towel) and turn the tap off with the towel to avoid possible recontamination. See facts about hand hygiene for more information.
  • If hand washing facilities are not available then use an alcohol-based gel.
  • Supervise children to make sure they wash their hands properly.
  • Make sure foods are thoroughly cooked.
  • Wash or peel all raw vegetables and fruits before eating.
  • Do not drink undisinfected water. Be wary of private supplies after flooding or other extreme weather events, especially if the water looks turbid (cloudy).
  • Wait at least 2 weeks after symptoms have ceased before entering a swimming pool or spa.
  • Always practice safe sex.

For travellers visiting remote areas of Australia or overseas:

  • Always make sure that your drinking water is safe to drink. If you suspect the water supply may be contaminated or untreated, boil it for one minute before drinking.
  • Do not consume ice, unless you know the water it has been made from has been properly disinfected and the ice has been hygienically stored.
  • Avoid eating raw foods washed with tap water that hasn’t been boiled.
  • Only consume freshly cooked (hot) foods and beverages, bottled water from sealed containers, canned or tinned food that has been properly stored and fresh fruit and vegetables that you can peel.

Where to get help

  • See your doctor.
  • Visit a GP after hours.
  • Ring healthdirect Australia on 1800 022 222.


  • Giardia infection is a form of gastroenteritis (gastro).
  • Symptoms including diarrhoea and stomach cramps usually appear between 7 and 10 days after infection.

This publication is provided for education and information purposes only. It is not a substitute for professional medical care. Information about a therapy, service, product or treatment does not imply endorsement and is not intended to replace advice from your healthcare professional. Readers should note that over time currency and completeness of the information may change. All users should seek advice from a qualified healthcare professional for a diagnosis and answers to their medical questions.