Pinworms belong to which group of helminths?

• A. Cestodes
• B. Trematodes
• C. Nematodes
• D. Acanthocephalids

Answer: (C)

Pinworms are roundworms, so they belong to the nematodes group. Nematodes are unsegmented, elongate worms with a simple tubular digestive system, making them distinct from flatworms. Cestodes (tapeworms) are flat and segmented and absorb nutrients across their surface without a gut; trematodes (flukes) are also flat but leaf-shaped with complex life cycles and suckers; acanthocephalids have a spiny proboscis and a different anatomy. Pinworms, such as Enterobius vermicularis, are small, white, threadlike nematodes that inhabit the large intestine and cause perianal itching due to eggs laid around the anus, highlighting their nematode nature.