Cause and spread
- Cause
- The protozoan Giardia duodenalis.
- How it spreads
- By swallowing cysts passed in the faeces of infected animals, in contaminated water, food or soil. Cysts are hardy in the environment.
- People
- Some types of Giardia are shared between animals and people, although spread to people is thought to be uncommon. Wash hands after handling pets and faeces.
Signs to watch for
- Often none, especially in adults
- Soft, light-coloured, mucus-covered, foul-smelling stools
- Sometimes vomiting and weight loss
- Poor growth in young animals
Many diseases look alike. Only a laboratory test can tell them apart, so please see a veterinarian for any sick animal.
How it is diagnosed
Cysts or the parasites are looked for in faeces under the microscope or with a specific test. Because they are small and can be mistaken for other material, and are passed on and off, several samples may be tested. A direct smear can also show other parasites that cause diarrhoea.
- Usually the first testGiardia TestDetects Giardia in faeces.
- Usually the first testVomiting and Diarrhoea Panel (panel)Blood count with faecal tests and a Giardia test for gut upset.
- Supports the diagnosisFaecal Direct SmearA fresh smear can show the parasite and other causes of diarrhoea.
- Supports the diagnosisFaecal FlotationFinds worm eggs and cysts.
Prevention and control
- Remove faeces promptly and clean up the environment
- Provide clean water and keep pets away from soil and water contaminated by other animals
- Keep new puppies and kittens' bedding and areas clean
Where this information comes from
- Giardiasis (factsheet) · Center for Food Security and Public Health, Iowa State University
General information for animal owners and veterinarians, last checked October 2026. It does not replace the advice of your veterinarian, who should decide which tests and treatment your animal needs.