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The facts about Giardia

The facts about Giardia

What is Giardia?

Giardia is a protozoan parasite that infects the gastrointestinal tract of humans, mammals, birds and even amphibians. The parasite can cause severe symptoms and is transmissible between animals and humans.

Giardia exists in two forms during its life cycle:

The trophozoite form: has unique flagella-like whips, enabling them to move through the intestinal tract with ease.
The cystic form: can survive several months in the environment, particularly in damp and wet conditions.
How is Giardia spread?

Dogs become infected with Giardia after they ingest the cysts, typically from contaminated water or grass. The cysts pass to the intestines and transform into the trophozoites, which then attach to the intestinal wall to feed. If there are significant numbers of the parasite, clinical signs of intestinal wall damage develop. These trophozoites reproduce, with some transforming into cysts. The dog eventually excretes the cysts in their faeces, completing the life cycle.

What are the symptoms of Giardia in the dog?

It’s important to note that not all dogs infected with Giardia show symptoms. Healthy adult dogs infected with Giardia will typically not have severe symptoms but may still shed cysts in their faeces. In younger, older or immunocompromised animals, symptoms may include:

Diarrhoea – can be intermittent
Foul-smelling faeces
Watery, mucousy, green or blood-tinged faeces
Weight loss
Diagnosis and treatment

There are different tests available to help diagnose infection with Giardia and we can advise you on the best one for your pet.

Treatment typically involves medication for 3-10 days. Some dogs may also require follow-up tests and repeat treatments.


Keep your pet’s environment dry and clean of faeces to help prevent infection. Pick up dog poo immediately and always apply proper hygiene. Wash your hands or use gloves to help reduce transmission onto humans.

If your dog has tested positive to Giardia, speak to us about how to disinfect your dog’s environment to help prevent ongoing reinfection.

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