Giardiasis is a diarrhoeal disease caused by infection with the protozoan parasite Giardia duodenalis. The parasite, previously known as both Giardia lamblia and Giardia intestinalis, is transmitted by direct contact with infected animals such as:

  • cattle
  • cats
  • dogs

It can also be transmitted from other infected people.

The consumption of food or water contaminated with faeces from infected animals can cause infection too. Swimming in contaminated water, such as lochs or rivers, may also cause infection.

Information about the symptoms and how to manage the Giardia infection is available by visiting the NHS inform website.


  • Guidance on the safe handling of food is available on the Food Standards Scotland website.
  • Information on reducing the risk of Giardia from the outdoors environment can be found on the NHS inform website.
  • The chance of infection can be reduced during travel by following advice on food and water precautions available on the fitfortravel website.

For all infection prevention and control guidance visit the A-Z ​pathogens section of the National Infection and Prevention Control Manual.

Data and surveillance