Giardiasis is a bowel infection caused by the parasite Giardia lamblia (also known as Giardia intestinatis).

How it is spread

Person to person spread occurs by eating food that has been contaminated by very small amounts of faeces from an infected person. 

Spread may also occur by ingesting Giardia from recreational water, drinking water or food contaminated by animal or human faeces. Giardia is not present in household drinking water in the Northern Territory.


The symptoms develop between 3 to 25 days or longer after infection, most commonly 7 to 10 days.

Symptoms of giardiasis include sudden onset of diarrhoea or foul smelling, pale, greasy stools (bowel action), stomach pains, bloating, loss of appetite, nausea, fatigue, weight loss, or poor weight gain in infants. The diagnosis of Giardia is confirmed by testing stools in the laboratory.

Some infected people may have no symptoms at all.

Infectious period

While the Giardia parasite remains in their faeces, infected people can pass the infection on to others. This can be for many months. Some people may ‘carry’ the parasite in their bowel after the symptoms have resolved or they may not have had any symptoms at all. 

Who is at risk

Children are infected more frequently than adults. Children who attend childcare facilities are at greater risk of infections spread through faecal contamination. Spread occurs when children share toys or food that has become contaminated and place it in their mouths.

Drinking unfiltered surface water (e.g. from creeks or billabongs) or swimming in bodies of freshwater increase the risk of contracting giardiasis.

Travellers to developing countries or remote communities where sanitation and hygiene standards are poor are at higher risk of contracting giardiasis.


Anyone with symptoms suggestive of giardiasis should be seen by a doctor. Antibiotics such as tinidazole or metronidazole may be prescribed.

Management focuses on preventing and treating dehydration caused by vomiting or diarrhoea. Anyone with vomiting or diarrhoea should drink extra fluids to avoid dehydration. Rehydration therapy with oral glucose / electrolyte solution is particularly effective. If children refuse this solution, diluted fruit juice drinks may be given (1 part juice to 4 parts water).

Babies should continue to be offered their normal feeds plus extra fluids in between feeds.

Children with diarrhoea, who vomit or who refuse extra fluids should see a doctor. Anyone with prolonged or severe diarrhoea or who have symptoms causing concern should see a doctor.

Medicines to prevent vomiting or diarrhoea should not be given, especially to children, except when prescribed by a doctor.


Good hygiene is the best way to prevent giardiasis.

Hands should be washed thoroughly with warm soapy water:

  • after going to the toilet
  • before preparing or handling food
  • after every nappy change
  • after changing soiled linen.

Other measures include:

  • never changing nappies on tables or counters where food is prepared or eaten
  • cleaning change areas with warm soapy water and disinfectant after every nappy change
  • not drinking untreated water
  • cleaning books, toys, equipment, furnishings, floors and toilets regularly (including toilet door handles)
  • washing and/or peeling fruit and vegetables before eating them
  • frequent emptying of wading pools. Pools should be cleaned and left to dry and not be used by children who have diarrhoea.

How it can be controlled

Anyone with diarrhoea should not attend childcare/school until there have been no loose stools for 24 hours. People with diarrhoea should not prepare or handle food that will be eaten by others. 

Anyone with diarrhoea should not swim, wade or paddle in public pools.

Doctors and public health workers are interested in preventing outbreaks of diarrhoea. If there are 2 or more cases of diarrhoea in a group, these should be reported to the local Centre for Disease Control.


For more information contact your nearest Centre for Disease Control.

Last updated: 12 May 2016

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