Guide to Parasitic Roundworm Diseases

by National Institute of Health

A parasite is an organism that exists by depending on another organism. Parasites that infect humans are much more widespread than many of us realize. These diseases affect not only poverty-stricken peoples in remote areas of the world, but they also can be important health problems for people throughout the world, including the United States.

As with other parasitic diseases, roundworm infections are more common in warm climates than in cooler, temperate areas. Many roundworm parasitic diseases result from human carelessness and a lack of appropriate personal hygiene and sanitation measures. Thus, the best solution to the problem rests in preventing these infections rather than in curing them.

Roundworms, or nematodes, are a group of invertebrates (animals having no backbone) with long, round bodies. They range in size from those plainly visible to the naked eye to those several hundredths-of-an-inch long and visible only under a microscope. Most roundworm eggs or larvae are found in the soil and can be picked up on the hands and transferred to the mouth or can enter through the skin. With the exception of the roundworm that causes trichinosis, mature adult roundworms eventually end up or live in human intestines and cause a variety of health problems.

Some of the most common parasitic roundworms in humans are Enterobius vermicularis, the pinworm that causes enterobiasis, Ascaris lumbricoides, the large intestinal roundworm that causes ascariasis, Necator and Ancylostoma, two types of hookworms that cause ancylostomiasis, Trichuris trichiura, the whipworm that causes trichuriasis, Strongyloides stercoralis that causes strongyloidiasis, Trichinella spiralis that causes trichinosis.

We discuss roundworms that infect human intestines only in this fact sheet.

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, affecting up to one-third of children in some areas. 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 3 to 6 weeks to complete.

How do pinworms get into the body?

Pinworms enter your 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 if you are infected and then scratch the contaminated area (the area around the anus where the female worm deposits her eggs), transferring the eggs to your fingertips and from there to your mouth. The eggs may be scattered into the air from bed linen and clothing, and can cling to doorknobs, furniture, tubs and faucets, and even food. Although you may have no symptoms over a long period, episodes of infection may return repeatedly.

Folklore is filled with fantastic descriptions of symptoms and abnormal behavior blamed on pinworm infection. Actually, 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.

Diagnosis

Your health care provider 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.

Prevention

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.

Treatment

Some health care providers believe that treatment is not 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 your health care provider does prescribe medicine, all members of your household should take it, regardless of whether they have symptoms. Medicines such as mebendazole and pyrantel pamoate (Povan) are the most useful in treating pinworm infections.

To relieve intense itching that often accompanies pinworm infection, your health care provider may prescribe a soothing ointment or cream.

About the Author

NIH is the nation's medical research agency - making important medical discoveries that improve health and save lives. The National Institutes of Health (NIH), a part of the U.S. Department of Health and Human Services, is the primary Federal agency for conducting and supporting medical research.