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Giardiasis is an infection spread mainly through food and water that causes diarrhoea that can last for a long time.

Recommendations for Travellers

The chance of infection can be reduced by following Food and Water Precautions during travel.  If you cannot access clean drinking water during your trip, for instance if you are trekking or climbing, you should be aware of safe water purification techniques.

Be aware of the risk of giardiasis if swimming or bathing in lakes, rivers and streams and try to avoid swallowing water whilst swimming.

There is no vaccine against Giardia.

Overview of the Disease

Giardiasis is caused by the microscopic parasite Giardia lamblia. The infectious form of the parasite is a cyst and it is present in the diarrhoea of an infected person.  The cyst is relatively resistant to chlorine and can survive for months in water that is not fully chlorinated, including in lakes and rivers. 

Infection occurs mainly by drinking water contaminated by parasite cysts, including unintended ingestion during swimming or bathing.

Infection can also occur:

  • after eating food contaminated by the parasite cysts – infection has occurred after eating meat, shellfish, dairy products, fruit and vegetables
  • from contact with the faeces of a person infected with Giardia, for example from touching a surface that has had faeces on (even if not visible) and then placing hands in mouth during eating, or during oro-anal sex.

Giardia occurs worldwide but is particularly common in areas with poor hygiene and sanitation facilities in South Asia, the Middle East and Central/South America and Caribbean.

The illness

Symptoms usually start 1 to 3 weeks after the parasite is ingested. Infection causes watery diarrhoea that can last for weeks to months.  Often the diarrhoea ‘floats’ in the toilet bowl as it contains undigested fat. Feeling sick, being sick, loss of appetite, tummy cramps, bloating, wind and weight loss can also occur.

After the infection has resolved some people may suffer from irritable bowel like symptoms that can last a long time.


The infection can be diagnosed on a sample of diarrhoea, but often it is diagnosed by the symptoms alone. It is treated with a course of antibiotics.

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