A species of Giardia found in humans, transmitted by ingestion of cysts in fecally contaminated water or food. In current usage, the preferred name for G. lamblia is now G. duodenalis. These organisms are found world wide. The most common symptoms of G. duodenalis infection are diarrhea, fever, cramps, anorexia, nausea, weakness, weight loss, abdominal distention, flatulence, greasy stools, belching, and vomiting. Onset of symptoms begins about 2 weeks after exposure; the disease may persist for up to 2 to 3 months.
A species of protozoa possessing a flagellum-like tail that invades the human gastrointestinal tract, leading to the onset of giardiasis. It is noteworthy that this protozoan does not disseminate to other bodily regions.