A 45-year-old man who emigrated from the Baltic region and habitually eats raw smoked fish presents with progressive numbness of the feet, glossitis, and macrocytic anemia with low serum vitamin B12 levels. Stool examination shows operculated eggs and broad proglottids that are wider than they are long. The causative organism is:

• A Taenia saginata
• B Diphyllobothrium latum ✓
• C Hymenolepis nana
• D Echinococcus granulosus

Explanation

Diphyllobothrium latum, the fish tapeworm, is the longest human tapeworm and competes for vitamin B12 in the ileum, producing megaloblastic anemia that may resemble pernicious anemia but with normal gastric acid. Its proglottids are broader than long, hence the species name latum, and its eggs are operculated, unlike the round eggs of Taenia species. Taenia saginata causes no B12 deficiency and its uterus is branched, not rosette-shaped.

Reference: Paniker's Textbook of Medical Parasitology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.