Giardia duodenalis
Giardia duodenalis is a flagellated protozoan parasite that colonizes the small intestine of humans and other animals, causing giardiasis.
Giardia life cycle: The sequence in which Giardia trophozoites multiply in the intestine and form environmentally resistant cysts. Cysts transmit infection; they release trophozoites after reaching the small intestine.
Diplomonad: A group of unicellular eukaryotes characterized by paired nuclei and reduced cellular structures. Giardia belongs to this group, whose distinctive cell plan informs its classification.
Stool antigen test: A diagnostic assay that detects pathogen proteins in a fecal sample. It can identify Giardia infection without relying on visual recognition of parasites.
Giardia muris: A Giardia species that primarily infects rodents and is used in some laboratory studies. It is a related species, unlike G. duodenalis, which infects humans and many mammals.
Giardia cyst: The environmentally resistant, infectious stage of Giardia, shed in feces and able to survive outside a host. This stage lets the parasite pass between hosts through contaminated water or food.
Flagellum: A long, whip-like cellular structure used for movement or sensing. Giardia trophozoites have multiple flagella that contribute to motility.
Ova and parasite examination: Microscopic examination of stool for parasite eggs, cysts, and other forms. Repeated specimens may reveal Giardia cysts shed intermittently.
Entamoeba histolytica: An intestinal amoeba that can cause invasive amoebiasis and dysentery. It is another protozoan cause of intestinal illness, but differs in morphology and tissue invasion.
Giardia trophozoite: The motile, replicating form of Giardia that inhabits the small intestine. Trophozoites attach to intestinal surfaces and multiply during infection.
Eukaryote: An organism whose cells contain a nucleus and other membrane-bound compartments. Giardia is a eukaryotic parasite despite its unusually reduced cellular features.