An ovum measuring about 70 by 38 μm with a thin shell is most consistent with which parasite?

• A. Ascaris lumbricoides
• B. Hookworm
• C. Diphyllobothrium latum
• D. Taenia solium

Answer: (B)

Recognizing parasite eggs by size and shell characteristics is key. An ovum about 70 by 38 μm with a thin shell fits hookworm eggs best. Hookworm eggs are typically in the 60–75 μm long range and around 40 μm wide, with a relatively thin, smooth shell. Ascaris eggs are similar in size but have a thick, mammillated shell that’s more rugged in appearance. Diphyllobothrium latum eggs are usually identified by an operculum (a lid-like end), not just a thin shell. Taenia solium eggs are smaller and have a thick, radially striated shell. So the measured size plus the thin shell most strongly points to hookworm.