What is Giardia?

Giardia is a protozoan parasite that can infect the intestinal tract in people and animals. It is not a worm, bacteria, or virus; it is a single-celled organism.

The Giardia organism has two forms. A fragile feeding form, a trophozoite, exists in the gut of the infected animal, while a hardy cyst form is shed in feces and can survive in the environment for several months. It is found on surfaces or in soil, food, or water that has been contaminated with feces from infected humans of animals.

Clinical Signs Include:
  • soft to watery stool (often containing blood and a greenish tinge)
  • excess mucous in the stool
  • in some cases vomiting
  • gradual weight loss

How is giardia contracted?

A dog is infected by swallowing the cyst stage of the parasite. Two trophozoites emerge from each cyst and attach to the intestinal wall and feed. Eventually, the dog passes cysts in the stool. These cysts are then able to infect another animal or human. Giardia can be transmitted by eating or sniffing the cysts from contaminated ground or by drinking contaminated water.

How is giardia diagnosed?

Direct smear of feces

How is giardia treated?

There are several prescription medications available that are effective at treating giardiasis.

  • metronidazole (most commonly)
  • tinidazole
  • nitazoxanide

Can I get giardia from my pet?

Yes, giardia infects nearly 2% of adults and 6 to 8% of children in developed countries worldwide. It is the most common intestinal parasitic disease affecting humans. In children, severe giardiasis might delay physical and mental growth, slow development and cause malnutrition.