Which feature distinguishes Hymenolepis nana from all other cestodes infecting humans?

• A It requires a copepod as the obligatory second intermediate host
• B Its eggs are operculated and unembryonated when passed
• C It can complete its entire life cycle in a single human host without any intermediate host ✓
• D It produces vitamin B12 deficiency by absorbing the vitamin through its proglottids

Explanation

Hymenolepis nana, the dwarf tapeworm, is the only cestode that needs no intermediate host: the hexacanth embryo penetrates the intestinal villus directly, develops into a cysticercoid, and returns to the lumen as an adult, allowing internal autoinfection and heavy worm burdens. Option A describes Diphyllobothrium, option B describes Diphyllobothrium latum eggs, and option D is also a property of D. latum, making those distractors factually true statements about other parasites but wrong for this question.

Reference: Paniker's Textbook of Medical Parasitology, 9th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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