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.

Visit NHS Inform for information about the symptoms and how to manage Giardia infection and how you can reduce the risk of infection in the outdoors environment.


Visit the Food Standards Scotland website for information on the safe handling of food.

If you are travelling, the fitfortravel website gives advice on avoiding giardia as well as how you can reduce the chance of infection by following their food and water precautions.

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

Data and surveillance

Surveillance reports

Data tables

Giardia, Scotland: annual totals as at 21 January 2022
  2011 2012 2013 2014 2015 2016 2017 2018 2019 2020*
Giardia species 195 186 157 158 186 223 269 199 210 112


* 2020 data remains provisional

Data source: Public Health Scotland