Author(s): Rebecca Chancey, Mary Kamb

Infectious Agent

Enterobiasis is caused by the intestinal nematode (roundworm) Enterobius vermicularis.

Transmission

People become infected, usually unknowingly, by ingesting infective pinworm eggs. Person-to-person transmission of infective pinworm eggs occurs through the fecal–oral route (including self-inoculation) by contaminated hands or eating contaminated food (rarely), or indirectly by handling bedding, clothing, or other articles contaminated by eggs. Because of their small size, pinworm eggs can become airborne, suggesting inhalation from air and dust could be another transmission route.

Epidemiology

Pinworm is endemic worldwide and commonly clusters within families. Infections are typically in preschool- and school-age children, people who care for young children, and people who are institutionalized. Based on limited data, travelers could be exposed in crowded conditions with infected people or through contaminated bedding.

Clinical Presentation

The incubation period is usually 1–2 months; successive reinfections might be needed before symptoms appear. The most common symptom is perianal itching, which can be severe, causing sleep disturbances and irritability. Secondary infection of irritated skin also can occur. Adult worms can migrate from the anal area to the urethra, vagina, vulva, or other sites. Appendicitis and enuresis are reported as possible associated conditions.

Diagnosis

Adult worms might be visible near the anus 2–3 hours after the infected person is asleep. Visual inspection of undergarments or bedding also might reveal pinworms. For microscopic identification, pinworm eggs can be collected by touching transparent tape to the affected person’s anal area immediately after awakening and before washing, ideally on 3 consecutive mornings. Eggs also might be found in samples taken from under fingernails before handwashing. Examining stool samples is not recommended because pinworm eggs are sparse. Diagnostic assistance is available through the Centers for Disease Control and Prevention (CDC)’s DPDx laboratory in the Division of Parasitic Diseases and Malaria.

Treatment

Drugs of choice are albendazole, pyrantel pamoate, or mebendazole given as a single, initial dose, followed by a second dose of the same drug 2 weeks later to eliminate possible reinfection. Pyrantel pamoate is available without prescription in the United States. Mebendazole is available in the United States only through compounding pharmacies. Simultaneous treatment of all household members is warranted if >1 person is infected, or infection recurs. Offer treatment to exposed sexual partners.

Prevention

Careful hand hygiene is the most effective prevention method. During treatment, change bed linens and underclothing of infected children first thing in the morning. Advise patients and families to collect linens and clothing carefully to avoid contaminating the environment (e.g., not shaking out the clothing or linens), and then laundering promptly in hot (>40o C) water and drying in a hot dryer to kill any eggs that might be present. To prevent transmission or reinfection, counsel infected people to bathe (shower or stand-up baths) in the morning and change underwear daily and bed clothes frequently, including after treatment and preferably after bathing. Infected people should also practice personal hygiene measures, including washing hands with soap and water before eating or preparing food, keeping fingernails short, avoiding scratching the perianal region, and avoiding nail biting.

CDC website: Pinworm