Parasitology Diagnostic Laboratory

Giardia lamblia

The image below is a cyst of Giardia lamblia, the most common parasitic protozoon of humans. Giardiasis occurs worldwide and is more prevalent in children than in adults. Trophozoites are pear-shaped and measure 10-20 µm. They have two nuclei, 4 pairs of flagella, two axonemes, and two median bodies. Infective cysts like this one are 11-15 µm long and oval-shaped. They contain 4 nuclei, filaments, and median bodies near the anterior end. Infection occurs by fecal-oral contamination.