|PARASITES - Protozoa |
Giardia lamblia cysts
Giardia lamblia is the protozoan that causes giardiasis, with its accompanying severe diarrhea, abdominal discomfort, malabsorption, and/or weight loss. Outbreaks occur often in the United States due to consumption of impure water containing Giardia cysts. The cysts are somewhat resistant to chlorine. Boiling of water and/or filtration are normally required to kill them. Because Giardia may be acquired by drinking water in the wilderness without purification, its common name is "backpacker's parasite". |
Giardia moves with flagella, placing it in the class Mastigophora.Cysts of Giardia lamblia are shown at 1000 X magnification in fecal material. Each cyst has an oval shape and usually two to four nuclei. The nuclei of Giardia may contain a central karysome that stains darkly. An axostyle, appearing like a dark line through the center of the cyst, may be visible. Parabasal bodies may also appear as comma-shaped structures. Diagnosis depends on finding cysts or trophozoites (trophs) in the stool.