Giardiasis is an infection mainly of the small intestine caused by the parasite Giardia lamblia. Giardiasis has been reported in humans and in a variety of animals. To prevent infection wash hands thoroughly and don't drink untreated water.

Last updated: 01 July 2012
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What is giardiasis?

  • Giardiasis is an infection mainly of the small intestine caused by the parasite Giardia lamblia. Giardiasis has been reported in humans and in a variety of animals.
  • Giardiasis can affect anyone; however, it is more common in infants, young children and young adults.

What are the symptoms?

  • 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.

How is it spread?

  • The Giardia organism is present in the faeces of infected humans and animals. Infection occurs when a person comes into contact with faecal matter and ingests the parasite.
  • Transmission is most likely to occur if hands are not washed after going to the toilet or after changing nappies; by drinking contaminated water; by swimming in contaminated pools; by handling infected animals; and through eating food contaminated by an infected person.
  • Transmission most often occurs through person-to-person contact, in settings such as households and child care centres.
  • Transmission can occur in some sexual practices.

Who is at risk?

Those most at risk of contracting giardiasis are:

  • People in contact with infected children, such as other children, parents, and child care workers
  • People who drink contaminated water, such as hikers and campers.

How is it prevented?

To avoid catching giardiasis:

  • Always wash hands thoroughly with soap and running water after: using the toilet, handling animals, changing nappies, other exposure to faecal matter, working in the garden; 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. Water purification tablets may kill Giardia, but may not kill other parasites. Some water filters may also remove these parasites
  • Avoid consuming unboiled tap water and uncooked foods when travelling in countries where the water supply may be unsafe.

To avoid spreading giardiasis:

  • Keep small children who have diarrhoea home from preschool, child care, and playgroups for 24 hours after their diarrhoea has completely stopped.
  • Do not prepare food or drink for others while you have symptoms
  • Do not use swimming pools for at least two weeks after diarrhoea has completely stopped
  • Do not share linen, towels and eating utensils with others while you have symptoms.

How is it diagnosed?

Giardiasis can only be accurately diagnosed through an examination of the faeces, by a test that is ordered by a doctor. See your doctor if you have symptoms.

How is it treated?

It is important for people with diarrhoea to drink plenty of fluids to avoid dehydration. Prescription drugs, including metronidazole and tinidazole, are used to treat giardiasis.

What is the public health response?

Giardiasis is a notifiable condition in NSW. Laboratories confirming diagnosis must notify public health units, who take action to prevent further spread of infection. All notifications are confidential.

For further information please call your local Public Health Unit on 1300 066 055