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Roundworm (Ascariasis)

A large roundworm, Ascaris lumbricoides is the cause of a parasitic infection of the small intestines called ascariasis. Humans are the preferred hosts for this parasite. Children become infected with this disease more often than adults. The illness often develops after a child puts his hands in his mouth after playing in soil contaminated by feces containing the roundworm eggs. Eating unwashed fruit or vegetables that were grown in contaminated soil can also cause ascariasis. Although the infection can occur in any part of the world, it is more common in developing countries with poor sanitation and areas where human feces are used as fertilizer.

The entire life cycle for this parasite occurs within humans. The adult worm in the bowels of a child lays thousands of eggs a day, which then pass into the stools. In areas with poor sanitation or where human feces are used as fertilizer, the eggs will mature for 2 to 3 weeks in the soil and become infectious on the surface of unwashed fruits or vegetables. If a child plays in the contaminated soil, he can get the eggs directly onto his fingers and put his fingers into his mouth, or a person could eat the parasite’s eggs that may end up on the surface of unwashed vegetables. After the eggs hatch in the bowel, the larvae burrow through the bowel wall and into the bloodstream. The blood carries the larvae to the lung, where the parasites can enter the breathing sacs. The larvae then crawl up the breathing tubes and into the throat, where they are swallowed. Once they are back in the gut, the larvae mature to adult worms.

Signs and Symptoms

Most children with A lumbricoides infections do not have any signs and symptoms. Sometimes youngsters have stomach cramps and, in the more serious cases, even intestinal obstruction that could lead to vomiting. Worms that travel into the bile ducts can cause blockage and infection of the liver, pancreas, or both. When the roundworm’s larvae migrate through the lungs, they can cause an allergic lung inflammation (pneumonitis) along with fever, cough, and wheezing. Sometimes, the worms are seen coming out of the anus, mouth, or nose.

When to Call Your Pediatrician

Contact your pediatrician if your child has any of the symptoms or signs described here, especially if they continue to get worse. Let your doctor know if your child has traveled to parts of the world where parasitic infections are common (ie, areas of poor sanitation, the tropics).

How Is the Diagnosis Made?

Most often, this infection is diagnosed by seeing a worm or worms in the diaper or toilet bowl or detecting eggs in a sample of your child’s stool. The eggs are microscopic in size, while the worms are several inches in length and have an appearance similar to an earthworm.


To treat A lumbricoides infections, your pediatrician may prescribe a single dose of medicine called albendazole or 3 days of pyrantel or mebendazole. These treatments should be given whether the infection causes symptoms.

Surgery is occasionally needed to relieve an intestinal or bile duct blockage.

What Is the Prognosis?

With proper treatment, children fully recover from ascariasis.


Reinfection is common. Keep your child away from soil that could be contaminated with human feces. Make sure you wash vegetables and fruits prior to eating.

Last Updated
Immunizations & Infectious Diseases: An Informed Parent's Guide (Copyright © 2006 American Academy of Pediatrics)
The information contained on this Web site should not be used as a substitute for the medical care and advice of your pediatrician. There may be variations in treatment that your pediatrician may recommend based on individual facts and circumstances.
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