Giardiasis — DTM&H MCQ

Correct answer: A — Giardiasis

The correct answer is A, Giardiasis. Giardia lamblia is acquired by ingesting cysts in contaminated fresh water, including untreated mountain streams, and causes malabsorptive symptoms with bloating, flatulence and pale, foul-smelling, greasy stools due to duodenal mucosal disruption and fat malabsorption, without fever or blood. The absence of systemic upset or dysentery, combined with the classic steatorrhoeic stool and a clear untreated-water exposure, is the discriminating pattern that points to Giardia rather than an invasive or systemic pathogen. Why the other options are wrong: B. Strongyloidiasis: acquired by larval skin penetration from contaminated soil, not water ingestion, and typically causes cutaneous larva currens, abdominal pain or eosinophilia rather than greasy bloating diarrhoea. C. Amoebic dysentery: caused by Entamoeba histolytica and classically presents with bloody, mucoid stool and lower abdominal cramping, features explicitly absent here. D. Enteric fever: caused by Salmonella typhi or paratyphi, transmitted via contaminated food or water but presenting with prolonged high fever, relative bradycardia and constipation or diarrhoea, not isolated greasy malabsorptive stool without fever. E. Cholera: causes profuse watery rice water stool leading to rapid dehydration, a very different pattern from the gradual, bloating, fatty diarrhoea described. Key point: Greasy, foul-smelling, bloating diarrhoea without fever or blood after untreated freshwater exposure is the classic exam pattern for giardiasis.

Reference: Patient.info (Egton Medical Information Systems, reviewed clinically), 'Giardia Infection: Causes, Symptoms and Treatment', https://patient.info/travel-and-vaccinations/travellers-diarrhoea-leaflet/giardia