Which parasite is commonly associated with water and can cause giardiasis?

• A. Cryptosporidium parvum
• B. Cyclospora cayetanensis
• C. Taenia saginata
• D. Giardia duodenalis

Answer: (D)

Giardia duodenalis is the parasite most commonly linked to water and giardiasis. It forms hardy cysts that can survive in water for long periods, so ingesting contaminated water from lakes, rivers, or untreated sources can readily lead to infection. Once inside the intestine, it causes symptoms like diarrhea, abdominal cramps, bloating, and weight loss. The infection is diagnosed with stool tests that detect Giardia antigens or cysts, and treatment typically involves anti-protozoal medication such as metronidazole or nitazoxanide.

Other organisms listed can be water-related but they cause different illnesses: Cryptosporidium parvum can produce watery diarrhea as well, but it’s a different parasite; Cyclospora cayetanensis causes cyclosporiasis often linked to contaminated produce or water; Taenia saginata is a beef tapeworm acquired from undercooked beef, not from water or giardiasis.