Ascariasis, also known as roundworm infection, is caused by Ascaris lumbricoides. It's the most common type of intestinal worm infection, occurring worldwide. Most patients recover without treatment, but complications can occur when adult worms move into certain organs and multiply, resulting in blockage of the intestine.
A. lumbricoides is a large roundworm resembling an earthworm. It's transmitted to humans by ingestion of soil contaminated with human feces that harbor A. lumbricoides ova. Such ingestion may occur directly (by eating contaminated soil) or indirectly (by eating poorly washed raw vegetables grown in contaminated soil).
Ascariasis never passes directly from person to person. After ingestion, A. lumbricoides ova hatch and release larvae, which penetrate the intestinal wall and reach the lungs through the bloodstream. After about 10 days in pulmonary capillaries and alveoli, the larvae migrate to the bronchioles, bronchi, trachea, and epiglottis. There they are swallowed and return to the intestine to mature into worms.
Ascariasis is most common in tropical areas with poor sanitation and in Asia, where farmers use human feces as fertilizer. In the United States, it's more prevalent in the south, particularly among people ages 4 to 12.
Ascariasis produces two phases: early pulmonary and prolonged intestinal. Mild intestinal infection may cause only vague stomach discomfort. The first clue may be vomiting a worm or passing a worm in the stool. Severe infection, however, causes stomach pain, vomiting, restlessness, disturbed sleep and, in extreme cases, intestinal obstruction. Larvae migrating by the lymphatic and the circulatory systems cause symptoms that vary; for instance, when they invade the lungs, pneumonitis may result.
CONFIRMING DIAGNOSIS The key to diagnosis is identifying ova in the stool or adult worms, which may be passed rectally or by mouth.
When migrating larvae invade alveoli, other conclusive tests include X-rays that show characteristic bronchovascular markings: infiltrates, patchy areas of pneumonitis, and widening of hilar shadows. In a patient with ascariasis, these findings usually accompany a complete blood count that shows eosinophilia.
Drug therapy, the primary treatment, consists of albendazole or mebendazole to kill intestinal parasitic worms, permitting peristalsis to expel them. No specific treatment exists for migratory infection because anthelmintics affect only mature worms.
In intestinal obstruction, nasogastric (NG) suctioning controls vomiting. If there's a blockage caused by a large number of worms, a paralyzing vermifuge (such as pyrantel pamoate or piperazine) can make the worms relax and pass through the intestine to relieve obstruction. However, ascariasis may necessitate surgery if the paralyzed worms result in intestinal blockage.
❑Although isolation is unnecessary, properly dispose of feces and soiled linen, and carefully wash your hands after patient contact.
❑If the patient is receiving NG suction, be sure to give him good mouth care.
❑Teach the patient to prevent reinfection with good hand hygiene, especially before eating and after defecation.
Review other book chapters online related to Ascariasis:
Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Professional Guide to Diseases (Eighth Edition) Authors: Springhouse Publisher: Lippincott Williams & Wilkins Copyright: 2005 ISBN: 1-58255-370-X 
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