An egg about 38 μm in diameter with a thick shell containing radial striations and several hooklets is seen in a wet mount. What is the most likely identification of the egg?

An egg about 38 μm in diameter with a thick shell containing radial striations and several hooklets is seen in a wet mount. What is the most likely identification of the egg?

• A. Hymenolepis nana
• B. Schistosoma japonicum
• C. Hymenolepis diminuta
• D. Taenia sp.

Answer: (D)

The main idea being tested is recognizing parasite eggs by their microscopic features—size, shell texture, and the internal embryo. An egg around 38 μm with a thick shell showing radial striations and an embryo bearing hooklets points to a Taenia tapeworm egg. The size fits the typical 30–40 μm range for Taenia eggs, and the thick, radiating shell (embryophore) is a hallmark you see with cestode eggs. The presence of multiple hooks (a hexacanth embryo with six hooks) inside is a classic clue that this egg belongs to Taenia species.

Other eggs in the choices have different characteristic appearances: some may be smaller or larger, lack the distinctive radial striations, or show different internal structures such as spines or polar features that aren’t described here. The combination of the size, thick striated shell, and six-hooked embryo makes Taenia the best match.