Giardia spp. are flagellates that inhabit which region of the host?

• A. Respiratory tract
• B. Gastrointestinal tract
• C. Circulatory system
• D. Muscular tissue

Answer: (B)

Giardia spp. are flagellated protozoa that live in the host’s gastrointestinal tract, primarily in the lumen of the small intestine. There they attach to the mucosal surface and reproduce, which can disrupt absorption and cause diarrhea and weight loss. They do not invade or reside in tissues of the respiratory tract, circulatory system, or muscular tissue, so those sites are not correct. Transmission is via cysts in contaminated water or food, highlighting their intestinal, luminal habitat.