Which nematode causes pruritus ani, particularly at night?

• A. Ascaris lumbricoides
• B. Strongyloides stercoralis
• C. Trichuris trichiura
• D. Enterobius vermicularis

Answer: (D)

Nighttime itching around the anus is classic for pinworm infection, caused by Enterobius vermicularis. The female worm climbs out of the intestine to lay eggs in the perianal skin during the night, which triggers intense itching. Scratching can transfer eggs to fingers, clothing, and surfaces, helping spread the infection, especially among children. Diagnosis is often made with a perianal swab or Scotch tape test to collect eggs. Other intestinal nematodes don’t produce this distinctive nocturnal perianal itch as a primary symptom: for example, Ascaris lumbricoides, Strongyloides stercoralis, and Trichuris trichiura cause other gastrointestinal or systemic issues rather than nocturnal anal pruritus. Treat with anthelmintics such as mebendazole or albendazole and ensure household-wide treatment and hygiene to prevent reinfection.