126. Which one of the following is the most accurate statement regarding giardiasis?
A. The drug of choice for giardiasis is chloroquine.
B. Giardia lamblia produces an enterotoxin that increases cAMP within the enterocyte, resulting in
diarrhea.
C. Giardia lamblia infection is acquired by ingestion of food or water contaminated with human
feces only (i.e. there is no animal reservoir for this organism).
D. Infection by Giardia lamblia occurs principally in the small intestine frequently resulting in the
malabsorption of protein and fat.

Detailed Explanation:

Correct Answer: D. Infection by Giardia lamblia occurs principally in the small intestine frequently resulting in the malabsorption of protein and fat.

Let’s examine why this is the most accurate:

• Giardia lamblia is a flagellated protozoan parasite that attaches to the lining of the small intestine, particularly the duodenum and jejunum.

• It does not invade the tissue but causes villous atrophy and enzyme disruption, which impairs absorption, especially of fats and proteins.

• This results in steatorrhea (fatty stools), bloating, and malabsorption syndrome.

Why the other options are incorrect:

• A. Chloroquine is used primarily for malaria, not giardiasis. The drug of choice for giardiasis is metronidazole or tinidazole.

• B. Giardia lamblia does not produce an enterotoxin. The pathology arises from mechanical interference with absorption, not a toxin-mediated cAMP pathway (unlike cholera).

• C. While fecal-oral transmission is common through contaminated water or food, animal reservoirs (e.g., beavers, dogs, and cats) are also recognized—so this is inaccurate.

Summary: Giardiasis primarily affects the small intestine and causes malabsorption, especially of fat and protein, making Option D the most accurate description.