By Dr. Karen Burgess

What exactly is Giardia?
Giardia is a parasite found in the intestine. Unlike other intestinal worms, Giardia is a one celled organism better known as protozoa. Animals coming from communal living situations (breeder, shelter, kennels) are commonly diagnosed with giardia infection.

What are the signs of Giardia infection?
Animals that test positive for Giardia can range from having no symptoms to being critically ill, dehydrated and with profuse diarrhea. Giardia found in adult animals showing no symptoms is not typically treated and is considered an insignificant finding. Essentially the healthy immune system keeps Giardia numbers under control preventing illness. It is often not even possible to clear Giardia from these pets. Young animals or immunosuppressed pets testing positive for Giardia are an entirely different situation. These pets are treated in an attempt to clear infection and avoid illness.

How do dogs and cats get Giardia?
Giardia is shed in fecal matter in the form of cysts. When another dog swallows these cysts they travel to the intestine and after several stages of development become infective.

How is Giardia diagnosed?
A microscopic examination of fecal matter will typically demonstrate Giardia cysts. Cell proteins of Giardia can also be tested for in the blood or feces via ELISA. Giardia cysts are very small and can be difficult to visualize; submission of specimens to a reference laboratory is often the most reliable testing method. Giardia cysts can be shed intermittently. If diarrhea persists in a patient retesting for Giardia via ELISA of fecal may be recommended.

What is the treatment for Giardia?
Treatment for Giardia usually involves metronidazole, fenbendazole, or in more resistant situations a combination of the two.

How can Giardia be prevented?
Giardia is found frequently in the environment making prompt removal of fecal matter essential to control. Cleaning surfaces with dilute bleach (one cup per gallon of water) and drying will also kill cysts that are highly resistant that can survive for years in cold moist environments. Bathing at least once during treatment is also recommended to remove any cyst stuck to the fur. Avoid taking an infected pet to swim or communal dog areas in an attempt to minimize exposure to others.

Can humans contract Giardia?
Humans do contract Giardia, but a different strain than animals. There have been cases where pets have contracted human strain Giardia thus making it a zoonotic disease. The risk of human infection from animal strain Giardia is considered rare if not impossible having never been reported. This would be more of a risk for those that are immunocompromised. Drinking contaminated water (fresh or tap) is a common source of exposure for people to human strain Giardia. Care should be taken to avoid handling of fecal matter from infected pets. Contact your physician with any specific questions regarding Giardia in humans.