Which organism is the giant roundworm causing a common intestinal helminth infection worldwide?

• A. Ascaris lumbricoides
• B. Taenia solium
• C. Enterobius vermicularis
• D. Trichuris trichiura

Answer: (A)

Ascaris lumbricoides is the giant roundworm responsible for ascariasis, one of the most common intestinal helminth infections worldwide. This large nematode is transmitted by ingesting eggs found in soil-contaminated food or hands, which then hatch in the small intestine. The larvae migrate through the liver to the lungs and are coughed up and swallowed again, allowing the worms to mature in the intestine. Adults can reach substantial lengths, and heavy infections can lead to intestinal obstruction or nutritional problems, especially in children. The other organisms listed are different types of parasites with distinct presentations: Taenia solium is a pork tapeworm; Enterobius vermicularis is a small pinworm that causes perianal itching; and Trichuris trichiura is a whipworm that causes abdominal symptoms and diarrhea, but none are the giant roundworm.