Characteristics of Pinworms

Pinworms (Enterobius vermicularis), also referred to as threadworms, are small, white roundworms about the size of a staple. Pinworms sometimes infect the human colon or rectum. This parasitic infection, referred to as enterobiasis or oxyuriasis, represents the most common worm infection in the U.S. Pinworm infections can be very uncomfortable, but they are treatable and usually do not lead to lasting complications.

Life Cycle

• Mature pinworms lay eggs on the perianal folds, which causes intense anal itching. Scratching the perianal folds leaves pinworms in a person's fingernails, which a person then transfers to the mouth or to linens or other objects. Once ingested, pinworm larvae hatch in the small intestine and move to the colon. While people sleep, mature pinworms leave the colon and lay eggs on the perianal folds, repeating the cycle.

Transmission

• People may get pinworms by touching infected bedding, linens, clothes or food. School-age children most frequently develop pinworm infections. Pinworms cannot be transmitted from pets because humans are the only known hosts of the parasites. Infection from swimming pools is theoretically possible but very unlikely.

Symptoms

• Pinworm infection typically causes intense itching around the anus, which may lead to insomnia or irritability. The skin around the anus often becomes irritated or infected from scratching. Girls may experience vaginal discomfort caused by a worm in the vagina. Severe pinworm infections may cause weight loss or appetite loss. Some pinworm infections may not cause symptoms.

Diagnosis and Treatment

• Doctors usually diagnose pinworms by having caregivers press a piece of cellophane tape around the patient's anus before bathing or using the toilet. Doctors then examine the tape under a microscope, looking for eggs. Doctors treat pinworm infections with mebendazole or albendazole, which kill pinworms. Doctors typically treat the entire household because more than one family member is usually infected.

Prevention

• Prevent pinworm infections or recurrences by keeping your fingernails short and clean and washing your hands thoroughly with soap and warm water after using the toilet and before eating. Do not scratch the anus or bite your fingernails. While a family member is being treated for pinworms, clean toilet seats daily, clean bed linens twice a week and launder infected items in hot water.