Which parasite’s eggs are operculated and visible in stool with distinctive shape?

• A. Diphyllobothrium latum
• B. Taenia solium
• C. Entamoeba histolytica
• D. Giardia lamblia

Answer: (A)

Operculated eggs in stool point to Diphyllobothrium latum, the fish tapeworm. The hallmark is a lid-like operculum at one end of the egg, giving it a distinctive, elongated shape that is large enough to be recognized under light microscopy. Taenia solium eggs lack an operculum and have a thick, radial-surfaced shell with a hexacanth embryo. Entamoeba histolytica forms cysts or trophozoites, not eggs, and Giardia lamblia forms cysts that are not operculated either. So the operculated, distinctive eggs best identify the fish tapeworm.