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Giardia; protozoa; diarrhoea; giardiasis; diarrhoea; vomiting; nausea ;

Giardiasis ('gee-ar-dye-a-sis') is an infection of the bowel caused by a parasite called Giardia. Giardia infection is one of the most common illnesses caught from water worldwide.

Giardiasis causes abdominal (tummy) pain and diarrhoea. It is most common in toddlers and young children, and also their parents and caregivers. It is also common in people who have travelled overseas especially to developing countries where the water supply is not safe.

More information

To findout more about Giardia you could look at these websites

Department of Health South Australia 
'Giardia infection - symptoms, treatment and prevention'

Better Health Channel
Gastroenteritis - giardiasis

Contents of this topic

What to do

  • Any child who has diarrhoea should be kept away from other children.
  • Giardiasis is treatable but to be sure that it is giardia, samples of the bowel action (poo) need to be examined. (The tests may need to be repeated before the diagnosis is certain).
  • If it is giardiasis a doctor can prescribe an antibiotic.
  • For ideas about how to manage the diarrhoea see the topic 'Gastroenteritis'.

What is giardia?

  • Giardia is a small single cell parasite which can live in the bowel of humans and many animals. It is not yet clear if humans catch giardia from animals.
  • Most giardia infections are caught from other humans either directly through contact with faeces (poo) or indirectly through drinking water which has the giardia in it or eating food which has the giardia on the surface.

Signs and symptoms of giardiasis

  • Some people with giardiasis do not have any symptoms, but others can become quite ill with tummy pain, bloating (feeling uncomfortably full), watery diarrhoea, very smelly bowel actions (poo) which often float on the surface in the toilet, nausea (feeling sick) and loss of appetite. Sometimes the person also has vomiting or weight loss.
  • This can settle down after a few days or weeks, but can go on as mild diarrhoea, loss of appetite and pain lasting for up to 6 weeks.
  • It may take up to 3 tests of bowel actions before the giardia is found as it is not passed in poo continuously. Over 95% of people with giardia will have it found if 3 bowel actions are tested, while less than 80% may be positive on one test.

Who is at risk?

  • In developed countries, such as Australia, most giardia illness occurs in young children. It is especially common in toddlers who are not yet toilet trained and who spend a lot of time with other toddlers (such as in child care). It can also affect their parents, other family members and care givers. But anyone can get giardia.
  • In some developing countries there is a lot of giardia in the water and on food, and people who live there can get repeated infections, but tend to no longer get symptoms from it. Visitors to the area can become quite ill. Overseas travellers who develop diarrhoea while travelling or after returning home often have giardia.

How long does it take to develop?

Generally it takes 1 to 2 weeks after exposure before the person becomes ill.

    Treating giardiasis

    People with giardiasis will become well without treatment, but they will go on having the parasite in their faeces for a long time, and can still spread the infection to others.

    • Treatment with metronidazole or tinidazole works very well, but should not be used in pregnant women. There are some alternative treatments.
    • Side effects are not frequent, but there can be metallic taste, nausea and loss of appetite.
    • If the treatments are taken at the same time as alcohol, there can be a drug interaction which includes nausea, vomiting, headache, abdominal cramps and flushing.

    Preventing the spread of giardia

    • Good hygiene, including thorough hand washing with soap and water is needed, especially when changing nappies and caring for young children.
    • If the water supply is not known to be safe, water should be boiled.
      • In the experience with giardia in the water in Sydney, it was recommended that water be boiled for 1 minute. Electric kettles often switch off after 20 seconds or less. They need to be restarted, or it can be better to boil the water on a cooktop.
      • Water supplied to homes in South Australia is checked regularly for giardia, and does not need to be boiled for normal use.
      • Do not drink water from lakes or streams that has not been boiled.
      • If you are unsure about the safety of water where you live you could ring the local water authority and check.
    • In areas where there may be giardia, it is recommended that all raw fruit and vegetables are washed in clean or boiled water and/or peeled before eating.
    • If you or your child has giardia, do not go swimming in pools, because you can still be passing the giardia for several weeks and it can get into the water. It is not always killed by the chlorine in pools.

    Giardiasis in child care, preschools and schools 

    • Make sure that any child who has diarrhoea is excluded from child care, preschool or school. (While children who do not have diarrhoea can still have the parasite in their faeces, it spreads more easily if they have diarrhoea.)
    • Make sure that all children and adults practice careful handwashing, so that they are able to do it well. (See 'Food safety' for more information).
    • Use disposable (paper) towels for drying hands.
    • Whenever possible make sure that the person who prepares food does not also change nappies. If this is not possible, the person who prepares food needs to be particularly careful when washing hands.
    • If gloves are used when changing nappies, hands still need to be washed after the gloves are taken off.
    • If possible keep children who are toilet trained separate from children in nappies.
    • Make sure that wee or poo does not leak from nappies by using plastic coated nappies, or well fitting plastic pants over the nappies.
    • Make sure that children who wear nappies have clothing over the nappies to prevent the children getting poo on their hands when they pull on the nappy.
    • Wash children's hands before they use water play tables or bowls.
    • Wash toys that can be put into the mouth of a child after each use.


    Department of Health South Australia 'Giardia infection - symptoms, treatment and prevention' 

    Center for Diseases Control and Prevention USA, 'Fact sheet: Giardiasis' (There is a lot of detailed information in this Fact sheet, plus other information for health professionals in related fact sheets.) 

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    The information on this site should not be used as an alternative to professional care. If you have a particular problem, see a doctor, or ring the Parent Helpline on 1300 364 100 (local call cost from anywhere in South Australia).

    This topic may use 'he' and 'she' in turn - please change to suit your child's sex.

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