Giardia and Pets

Giardia is a protozoal parasite common in humans and domestic animals worldwide. It comes in two forms: an active form (mobile trophozoite) that lives in the small intestine and a cystic form that is released from the intestinal tract and survives in wet conditions. It is contracted primarily from drinking contaminated water.

Giardia is the most common intestinal parasite worldwide, often causing gastrointestinal upset. Once a host (human, dog, cat, etc.) drinks contaminated water, the parasite makes its way to the small intestine and it can cause diarrhea. It is uncertain how it causes disease, but it appears that it is implicated in “flattening” or decreasing the absorptive surface of the fingers or villi of the small intestine. Symptoms are more commonly seen in young puppies and kittens but can occur in mature individuals as well, especially those that are physiologically stressed or immunocompromised.

Giardiasis can be diagnosed in dogs and cats by microscopically examining feces and/or performing specialized tests on feces. Once a patient is diagnosed, treatment can be initiated via oral medication, lifestyle and nutritional changes as necessary. Prognosis for complete recovery is quite high. However, symptoms may return especially if the source of infection is not identified and contaminated water is repeatedly ingested.

If your dog or cat is experiencing diarrhea, be sure to book an appointment with your veterinary health team to have your dog or cat examined and, if possible, bring in a fresh fecal sample to be analyzed.

Written by Rob Doucette, DVM