Giardiasis (gee-ar-dye-a-sis) is an infection of the digestive system caused by tiny parasites called Giardia intestinalis (also known as Giardia lamblia, or Giardia duodenalis).
Diarrhoea is the most common symptom of giardiasis. Other symptoms can include vomiting, abdominal cramps, bloating and foul-smelling wind. Although these symptoms are often very unpleasant, giardiasis doesn't usually pose a serious threat to health. It can be easily treated.
Read more about the symptoms of giardiasis.
When to see a doctor
You should visit your GP if you have symptoms of diarrhoea, cramps, bloating and nausea that last for more than a week.
Your GP may have to send some stool samples to be tested in a lab to confirm a diagnosis of giardiasis, but usually it's easily treated with medicine that kills the giardia parasite.
Read more about treating giardiasis.
How is giardiasis spread?
Most people become infected with giardiasis by drinking water that's contaminated with the parasite.
The giardiasis infection can also be passed on if an infected person doesn't wash their hands properly after using the toilet, then handles food that's eaten by others. Food can also be contaminated if washed with infected water.
Who is affected?
Giardiasis occurs almost everywhere in the world, but it's particularly widespread in parts of the world where access to clean water is limited and sanitation is poor.
It can affect people of all ages but it's most common in young children and their parents. This is because activities such as nappy changing increase the risk of infection.
There are around 3,000 cases of giardiasis reported in England and Wales each year. But the true number is likely to be higher as many cases go undiagnosed.
Around one third of cases in the UK are thought to be contracted abroad, but the person doesn't develop the symptoms until they return home.
Most cases of giardiasis are one-off, but small outbreaks can sometimes occur in households, among family members, or at nurseries. Larger outbreaks are usually traced to contaminated water sources, such as drinking wells or water parks.
