Pinworm Infection (Enterobiasis)

A pinworm is the most common roundworm parasite in temperate climates - even in areas with high levels of sanitation. In the United States, it is the most common of all parasitic roundworm infections, according to the National Institute of Allergy and Infectious Diseases (NIAID). It reportedly affects up to one-third of the country's children. Because pinworm infection is spread mainly by children, it is found most often in family groups, day-care centers, schools and camps.

Pinworms are small, threadlike roundworms found primarily in the colon and rectum. The life cycle of the pinworm - egg, larva and mature worm - takes place inside the human body and requires from three to six weeks to complete.

Pinworms enter the body when eggs are swallowed. The female pinworm expels thousands of eggs into the environment. Because the eggs are moist and a bit resistant to drying, they may be able to infect someone for several days after being distributed in dust. They can cling to the fingers of children.

Exposure to infective eggs may occur when the person who is infected scratches the contaminated area (the area around the anus where the female worm deposits her eggs) and then transfers the eggs to the fingertips and from there to the mouth. The eggs may be scattered into the air from bed linen and clothing, and can cling to doorknobs, furniture, tubs, faucets and even food. Although a person may have no symptoms over a long period, episodes of infection may return repeatedly.

Symptoms & treatment options

NIAID says the symptoms are usually mild and vague. Movement of egg-laden female worms from the anus will often produce itching of the anus or vagina that, in some cases, may become very intense and even interfere with sleep.

A doctor or other health care worker can diagnose pinworm infection by finding the eggs. The most common way to collect the eggs is a rather simple one involving swabbing the anal area with the sticky side of a piece of transparent cellophane tape. The tape is then transferred to a slide where it can be looked at under a microscope.

NIAID says you can prevent becoming infected or reinfected with pinworms by:

• bathing frequently
• using clean underclothing, night clothes and bed sheets
• washing your hands routinely, particularly after using the bathroom

Some doctors believe that no treatment is necessary for pinworm infections that have no symptoms. This is because children usually outgrow the infection. Because of the strong probability that small children will get infected again outside the home, strenuous efforts to eliminate the eggs from the household are of little help.

If the doctor does prescribe medicine, NIAID says all members of the household may need to take it, regardless of whether they have symptoms. Drugs such as mebendazole and pyrantel pamoate are the most useful in treating pinworm infections, according to NIAID.

To relieve intense itching that often accompanies pinworm infection, a doctor may prescribe a soothing ointment or cream.