What is Giardia Disease?

Giardia spp. are parasitic protozoans (single celled organisms) found in the intestines of many animals, including dogs. This microscopic parasite clings to the surface of the intestine or floats free in the mucous lining the intestine.

The prevalence of Giardia in dogs of Alberta is not known. However, rates of 5 to 10 per cent have been suggested. This level is consistent with those reported in surveys from the United States and many other countries.

What is the life cycle of Giardia?

Giardia occurs in two forms: a motile feeding stage that lives in the intestine a non-motile cyst stage that passes in the feces.

Encystment occurs as the parasite travels to the large intestine. The cysts are fairly resistant and can survive for several months as long as sufficient moisture is provided. Mature cysts are usually found in the feces of infected animals.

Animals become infected by ingesting cysts. These cysts break open in the intestine to release the motile feeding stage (trophozoite). Giardia increases their numbers by each organism dividing in half repeatedly by a process called binary fission.

What are the different kinds of species of Giardia?

Species of Giardia are morphologically similar. It was customary to give each Giardia a different name when it was found in a new host. For example, the Giardia in dogs was called Giardia canis, in cattle, Giardia bovis, and so on. Today, scientists believe that few species occur, and each species can infect more than one host. However, more research is needed on identifying each species and determining the hosts they can infect.