Giardia duodenalis is a protozoan flagellate (Diplomonadida). Cysts are resistant forms and are responsible for transmission of giardiasis. Both cysts and trophozoites can be found in the feces (diagnostic stages) . The cysts are hardy and can survive several months in cold water.

Giardia lamblia exists in two forms, an active form called a trophozoite, and an inactive form called a cyst. The active trophozoite attaches to the lining of the small intestine with a "sucker" and is responsible for causing the signs and symptoms of giardiasis.

Cyst: Oval cyst is thick-walled with four nuclei and several internal fibers. Each cyst gives rise to two trophozoites during excystation in the intestinal tract. Trophozoite: Pear-shaped with two nuclei, four pairs of flagella, and a suction disk are present.

· Giardia microti - Mostly affects voles and muskrats and is characterized by cysts that contain two trophozoites as well as mature ventral disks. However, when viewed under the light microscope, they possess morphological features similar to those of G. lamblia.

The laboratory diagnosis of Giardia spp. is mainly based on demonstration of microscopic cyst or trophozoite in stool samples but several immunological-based assays and molecular methods are also available for giardiasis diagnosis.

2011年5月4日 · Compared with many protists, Giardia lamblia has a simple life cycle alternating between cyst and trophozoite. Most research on the molecular biology of Giardia parasites has focused on trophozoites and the processes of excystation and encystation, whereas cysts have attracted less interest.

2022年2月26日 · Giardiasis can be diagnosed by the identification of cysts of Giardia lamblia in the formed stools and the trophozoites and cysts of the parasite in diarrheal stools. Macroscopic examination : offensive odor, are pale-colored and fatty and float in water.