Giardiasis is the intestinal disease caused by the parasite Giardia canis. Giardiasis usually affects dogs, particularly puppies, but can occur in cats. In North America, it’s fairly common in people too. It’s not so much that it is passed directly from animals to humans, but that both come into contact with the same contaminated water source, such as water from a well.
The majority of the parasite’s life cycle is spent in the intestines of its unwitting host. The parasite forms a hard cyst that gets passed in feces and is thus spread into the environment.
Diarrhea, severe or mild, is most common sign of giardiasis. The diarrhea can be either intermittent or chronic. Typically there is a high volume of diarrhea with soft, almost frothy, mucousy stools. Weight loss and malabsorption can occur. A rancid odor to the feces is often noticed. Usually the diarrhea goes away on its own and the pet is fine, but some severe cases can cause weight loss and general lethargy. The infection is diagnosed with a Giardia-specific ELISA test.