Giardia Overview


Spread of Giardia

Giardia are parasitic, single-celled organisms called protozoa that live in the small intestine of dogs. Giardia protozoa prevent nutrients from being properly absorbed through the dog’s small intestine. Many dogs carry the infection, but do not display the disease. While these dogs show no symptoms of infection, they are highly contagious.

Giardia is spread through the feces or poop of infected dogs. Dogs become infected with Giardia by consuming Giardia cysts when drinking contaminated water, grooming, or consuming anything that is contaminated with the cyst.

A Giardia cyst is a group of Giardia protozoa that has formed a protective protein shell around itself. Giardia cysts form inside the small intestine of the host and pass through the stool and into the environment. Giardia can be passed from dogs to humans through contaminated dog waste.

Symptoms of Giardia Infection

Dogs infected with Giardia may display severe symptoms or no symptoms at all. Symptoms include: diarrhea, gas, bloating and weight loss. Dog waste from infected dogs may appear greasy, have a foul odor, or be pale in color.

Dogs infected with Giardia may display symptoms very suddenly, or they may appear and reappear over a period of weeks, months, or even many years.

Diagnosis of Giardia

Diagnosis of Giardia is frequently performed by looking for Giardia cysts in the stool of an ill dog. This test is called a Fecal Coliform Test. Giarda cysts may not be present in all stool samples. Multiple dog waste samples are generally needed to determine if there is an infection.

A new and accurate method for determining Giardia infection is the Giardia SNAP test invented by IDEXX Laboratories. The Giarda SNAP determines in less than 10 minutes if the proteins used to create the protective cyst wall are present in the dog waste. If the protein is present, the dog is positively diagnosed for Giardia.


There are a number of drugs available to treat Giardia infections. Based on our research, there does not seem to be a clear determination on the best way to treat dogs infected with the Giardia protozoa. Further, many medications have side effects that include nausea, bone marrow injury and even birth defects.

Four commonly used drugs are:

  • Metronidazole – Metronidazole disrupts the DNA structure of the Giardia
  • Quinacrine hydrochloride
  • Fenbendazole – Fenbendazole is a member of the anthelmintics family and is used to expel Giardia cysts from the intestine. This family of drugs is more commonly used to treat intestinal worm infestations.
  • Albendazole

Prevention of Giardia Infection

The best way to prevent Giardia infection is to keep your dog away from the waste of infected animals. Giardia cysts can survive for months outside if the conditions remain cold and wet. The spring thaw tends to reveal many piles of poop that have not been picked up as diligently as one might hope. Since Giardia cysts can live for extended periods of time in cold and wet environments, it is logical to assume that parks this time of year will have a higher than normal population of Giardia protozoa. Keep an eye on your dog this time of year. Especially if you regularly visit dog parks and other public places shared by a variety of dogs. If your park or community has a problem with accumulated pet waste it may be wise to look into hiring a pooper scooper service. Services such as DoodyCalls pet waste removal can do a large “spring cleaning” of the community common areas to clean all the dog waste from paths, playgrounds and common areas.

A Canine Giardia vaccine is available but not recommended because, as the UC Davis Website states: “the diseases are either of little clinical significance or respond readily to treatment, evidence for the efficacy of these vaccines is minimal, and they may produce adverse events with limited benefit.”

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