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Enterobius vermicularis (Pinworm—Intestinal Nematode)

المؤلف:  Stefan Riedel, Jeffery A. Hobden, Steve Miller, Stephen A. Morse, Timothy A. Mietzner, Barbara Detrick, Thomas G. Mitchell, Judy A. Sakanari, Peter Hotez, Rojelio Mejia

المصدر:  Jawetz, Melnick, & Adelberg’s Medical Microbiology

الجزء والصفحة:  28e , p741

2026-03-12

532

 The Organism

 Female pinworms (about 10 millimeters in length) have a slender, pointed posterior end. Males are approximately 3 millimeters in length and have a curved posterior end (Figure 1A and B). Pinworms are found worldwide but more commonly in temperate than tropical climates. They are the most common helminthic infection in the United States and infect mostly children.

Fig1. Enterobius vermicularis. A: Adult female pinworm (10 millimeters in length). B: Adult male pinworm (3 millimeters in length). C: A Scotch Tape test reveals a pinworm egg (50–60 μm in length) with an infectious larva inside. (Used with permission from Sullivan J: A Color Atlas of Parasitology, 8th ed. 2009.)

Pathology and Pathogenesis

The main symptom associated with pinworm infections is perianal pruritus, especially at night, caused by a hypersensitivity reaction to the eggs that are laid around the perianal region by female worms, which migrate down from the colon at night. Scratching the anal region promotes transmission, as the eggs are highly infectious within hours of being laid (hand-to-mouth transmission). Irritability and fatigue from loss of sleep occur, but the infection is relatively benign.

Eggs are recovered using the “Scotch Tape” technique in the morning before a bowel movement. Transparent Scotch Tape is applied directly to the perianal area, and then placed on a microscope slide for examination. Eggs are football shaped, have a thin outer shell, and are approximately 50–60 μm in length (Figure 1C). Infectious larvae are often visible inside the egg. The small adult worms may be seen in a stool O&P (ova and parasites) test. Because the eggs are lightweight and highly infectious, it is important for bed linens, towels, and clothing to be washed in hot water to prevent reinfection.