In a child with intestinal worm exposure on a farm and abdominal bloating, which parasite is most likely to cause intestinal obstruction in a heavy infection?

• A. Ascaris lumbricoides
• B. Enterobius vermicularis
• C. Taenia saginata
• D. Hookworms

Answer: (A)

When a heavy worm burden causes a blockage, Ascaris lumbricoides is the classic offender because these large intestinal nematodes live in the lumen and can accumulate in large numbers to form a bolus that narrows or blocks the intestinal passage, especially at the ileocecal junction. Children are particularly at risk, and soil contaminated with eggs—such as from farm exposure—facilitates ingestion and heavy infection. Enterobius vermicularis mainly causes perianal itching and doesn’t obstruct the lumen; Taenia saginata is a tapeworm that typically causes milder GI symptoms and obstruction is rare; hookworms cause anemia and GI symptoms from mucosal irritation rather than luminal blockage. Thus the scenario points to Ascaris as the most likely cause of obstruction in a heavy infection.