Which nematode eggs are described as barrel-shaped with bipolar plugs?

• A. Ascaris lumbricoides
• B. Trichuris trichiura
• C. Necator americanus
• D. Enterobius vermicularis

Answer: (B)

Recognizing egg morphology helps identify the nematode. Barrel-shaped eggs with bipolar plugs are a hallmark of Trichuris trichiura, the whipworm. The ends protrude as polar plugs, giving a distinct barrel-like appearance, and the shell is thick and protective. This contrasts with other common nematode eggs: Ascaris lumbricoides eggs are round with a mammillated surface; Necator americanus eggs are oval with a thin shell and developing morula; Enterobius vermicularis eggs are small, ovoid with a flattened side rather than barrel-shaped with plugs. Thus, the described egg morphology points to the whipworm.