The Giardia Parasite in Dogs

A dog remains infectious with giardia for as long as parasitic cysts remain in his poop.


The protozoal parasite giardia in dogs can be a minor nuisance or a royal pain to treat and totally clear. Symptoms of giardia in dogs include diarrhea, maldigestion, and malabsorption. Diarrhea is often intermittent, based on the parasite’s life cycle. Giardia is contagious in dogs as long as giardia cysts remain in the feces. It can be difficult to clear the infection.

Diagnosis of Giardia in Dogs

Stools from dogs with giardia may be soft or watery or appear slightly green. Occasionally, blood or mucus may be noticed. Healthy adult dogs seem to be somewhat naturally resistant, while puppies may fail to thrive.

Diagnosis of giardia is generally by a fresh fecal exam or sending samples off to check for giardia antigens. Due to the intermittent shedding, the diagnosis can be missed, especially by fresh smears only.

Giardia Treatment

There is no FDA-approved treatment for giardia in dogs. Metronidazole and febendazole are often used off-label separately or together.

A dog may need repeated giardia treatments to totally clear the infection as some resistance appears to be developing. Symptomatic treatment for giardia diarrhea includes adding fiber to your dog’s diet until his stools are normal. Follow-up veterinary fecal checks for giardia are critical to ensure you have rid the dog of the giardia parasite.

Giardia Is Contagious

As long as viable giardia cysts are passed in the stools, your dog will remain contagious to other dogs and to a lesser extent to people. Assume that during the time your dog is being treated, he is contagious.

Clean up poop immediately and consider having any dog or puppy who is infected use a separate area for elimination. It can be worthwhile to check all dogs in the household if you are having trouble clearing an infection as some adults will be asymptomatic carriers.

Reinfection with Giardia

One of the problems with gaining control of a giardia infection is cleaning the environment to prevent reinfection. Bleach and Parvasol can be used to clean bedding and floors. Steam clean carpets. Bathe your dog to remove any fecal material or cysts on his coat.

Unfortunately, giardia cysts can survive outdoors for months in a moist environment. Direct sunlight and dry conditions will kill cysts. It can be difficult to clear giardia from shelters and sites like daycares once it gains a foothold.

Also known as “beaver fever,” giardia in dogs has been associated with dogs drinking water out on hikes in the woods, but it is common in urban dogs as well with municipal water systems taking the blame.