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An estimated 807-1,221 million people in the world are infected with Ascaris lumbricoides (sometimes called just "Ascaris"). Ascaris, hookworm, and whipworm are known as soil-transmitted helminths (parasitic worms). Together, they account for a major burden of disease worldwide. Ascariasis is now uncommon in the United States.

Ascaris lives in the intestine and Ascaris eggs are passed in the feces of infected persons. If the infected person defecates outside (near bushes, in a garden, or field) or if the feces of an infected person are used as fertilizer, eggs are deposited on soil. They can then mature into a form that is infective. Ascariasis is caused by ingesting eggs. This can happen when hands or fingers that have contaminated dirt on them are put in the mouth or by consuming vegetables or fruits that have not been carefully cooked, washed or peeled.

People infected with Ascaris often show no symptoms. If symptoms do occur they can be light and include abdominal discomfort. Heavy infections can cause intestinal blockage and impair growth in children. Other symptoms such as cough are due to migration of the worms through the body. Ascariasis is treatable with medication prescribed by your health care provider.

Image: Left/Right: Fertilized eggs of A. lumbricoides in unstained wet mounts of stool. Center: Adult female A. lumbricoides. Credit: DPDx, Orange County Public Health Laboratory, Santa Ana, CA.

  • Page last reviewed: May 24, 2016
  • Page last updated: May 24, 2016
  • Content source:
    • Global Health - Division of Parasitic Diseases and Malaria
    • Notice: Linking to a non-federal site does not constitute an endorsement by HHS, CDC or any of its employees of the sponsors or the information and products presented on the site.
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