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Giardia Giardia

What is giardiasis?

Giardiasis is an illness caused by a parasite (a tiny organism) called giardia. It causes diarrhoea which is often very smelly, causing cramping stomach ache and wind. The illness may last for several weeks; it then resolves slowly sometimes over several weeks. The incubation period (the time taken from swallowing the germs until the illness starts) is usually 7-10 days. However the duration of the illness can be variable and it may be chronic and recur.

It occurs world-wide but is particularly prevalent in the tropics. It is an important cause of traveller's diarrhoea.

Who is at risk?

Anybody can get giardiasis, but the illness can be more severe and prolonged in people with impaired immune systems. In the UK it is most common in children under 5 years old and young adults.

Many people have giardiasis (the disease caused by giardia) and show no symptoms - these are carriers of the infection. Others develop symptoms 1-2 weeks after ingesting the parasite. Symptoms include diarrhoea, often watery in the early stages of the illness, nausea (feeling sick), no appetite, abdominal pain and bloating.

How do I get giardiasis?

  • By swallowing the parasite that has been passed from the bowel of another person who already has the infection. This can happen especially if hygiene is poor.
  • From drinking untreated water which contains the parasite. This is more likely to happen abroad, and giardia is one of the causes of traveller's diarrhoea.
  • From contact with pets and animals that are infected, usually through poor hand washing.

How can I avoid getting giardiasis?

The most effective way to stop the spread of giardiasis is to wash hands thoroughly. This means taking care to wash palms, back of the hands, between the fingers, the fingertips and under fingernails.

How to wash your hands

  1. Using warm water and soap, wet your hands thoroughly and add soap to the middle of your palm
  2. Rub you hands together to make a lather
  3. Rub back of hands and fingers
  4. Rub in between fingers, round thumbs, fingertips and nails
  5. Rinse off with clean water
  6. Dry hands thoroughly on a disposable towel and turn the tap off using the towel before disposing of it.

Remember germs can hide under watches, rings and bracelets and these should be removed.

It is just as important to dry your hands after washing them as damp hands can spread 1,000 times more germs than dry hands. 

Always wash your hands thoroughly with soap and warm water and dry with a clean towel:

  • after going to the toilet
  • after changing a baby's nappy
  • after contact with pets and animals
  • before preparing and eating food


  • If on picnics with no water available to wash hands, use disposable travel wipes.
  • Only drink water from safe sources - if not sure, boil it first. Avoid drinking untreated water e.g. from streams and lakes.
  • Take extra care on visits to farms or the countryside to wash hands thoroughly.
  • Keep pets away from food, dishes and worktops.

How do I treat giardiasis?

If you have diarrhoea then drink plenty of fluids. Giardiasis is one of the few stomach bugs where antibiotics help. The treatment is usually with a drug called metronidazole, which your GP can prescribe. It is very important that you do not drink alcohol while you are having this treatment.

Do I need to stay off work, school or nursery?

Yes, until you have been completely free from any symptoms for 48 hours. Children should not play with other children or attend school or nursery until they are fully recovered and have been symptom free for 48 hours. If you work as a food handler, with young children or in healthcare, you must inform your employer and / or seek advice from the Environmental Health Department.

What should I do if a member of my household has giardiasis?

Ensure that you and all household members wash their hands thoroughly with warm water and soap:

  • After using or cleaning the toilet
  • After attending to another person who has diarrhoea/vomiting
  • After changing a baby's nappy
  • After handling or washing soiled clothes and bedding
  • Before eating or preparing food


  • Each person affected has their own towel for drying hands.
  • Ensure that young children are supervised when washing hands, or have their hands washed for them.
  • Wash soiled clothes, bedding and towels on a hot cycle of the washing machine. Keep soiled washing separate from the rest of the washing.
  • Clean toilet seats, flush handles and taps frequently with hot soapy water. The toilet bowl should be cleaned with a toilet brush and disinfectant. Wear rubber gloves to clean the toilet and keep them for this use only.
  • Where possible stay away from other people until your symptoms have stopped, especially vulnerable people like the elderly and very young.
  • Where possible, do not prepare food for your family or anyone else.

Further advice

If you have concerns about your health, please contact your family doctor or NHS Direct on Tel: 111 or visit NHS Direct. If you would like to know more about giardiasis and its cause, spread and control, please contact Environmental Health Services.

Information provided by the Health Protection Agency (HPA).


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