or G. intestinalis
Single-celled protozoan parasite.
Pear-or beet-shaped, the cells have two nuclei and eight flagella and attach with a sucking organ to human intestinal mucous membranes. They cause the disease giardiasis. Generally spread when traces of human feces containing the parasite are ingested, giardiasis is most common among children in close contact with other children, but it also occurs among adults. Diarrhea, pain, and distension of the stomach may occur. It is common wherever there is contamination of domestic or surface water in lakes, rivers, and reservoirs, and it is a major cause of diarrhea worldwide. Beaver feces are often responsible for giardiasis among campers who take water from lakes and rivers.