Ascariasis is an infection that causes problems in the lungs or bowels.

Digestive Tract and Lungs
Digestion tract and Lungs 3D

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A roundworm parasite causes ascariasis. The roundworm can grow to over 15 inches (40 centimeters) in length. Their eggs hatch in the stomach and the larvae travel to the liver and lungs. This causes a type of pneumonia. They get into the throat during coughing or working their way up. Once swallowed, they grow into adult worms in the stomach. Their eggs leave the body in the stool.

The cycle starts again when a person takes in food or drinks contaminated with stool that has eggs.

Risk Factors

Roundworms are most common in places with poor sanitation or sewage control. The risk of getting sick is highest in Asia and the western Pacific.

Risk is also higher if exposed to tainted soil or water. This can happen with:

  • Children who are preschool age or younger who play in it
  • Eating food grown in or washed in it
  • Drinking the water
  • Eating the soil


Most people not have symptoms. In those that have them, infection may cause:


  • Dry cough
  • Fever
  • Wheezing
  • Breathing problems


  • Belly cramps
  • Vomiting
  • Diarrhea
  • Weight loss

The worms can cause problems in the gallbladder, liver, pancreas, and appendix.

Inflammed appendix

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The doctor will ask about your symptoms. You will be asked about your health and travel history. A physical exam may point to roundworms. If needed, you may also have:

  • Stool tests
  • Blood tests
  • Imaging tests:


Medicines treat the roundworm parasites. Surgery can treat bowel obstruction.


Always wash your hands after using the bathroom.

When you travel to places where ascariasis is common:

  • Use bottled or boiled water.
  • Eat foods that are cooked through and hot.
  • Don’t eat raw fruits or vegetables that don’t have a peel.

Centers for Disease Control and Prevention

World Health Organization


Public Health Agency of Canada

Travel and Tourism—Government of Canada


Ascariasis. EBSCO DynaMed Plus website. Available at: Updated January 16, 2017. Accessed May 25, 2018.

Ascariasis. Merck Manual Professional Version website. Available at: Updated February 2017. Accessed May 25, 2018.

Parasites—ascariasis. Centers for Disease Control and Prevention website. Available at: Updated February 15, 2018. Accessed May 25, 2018.

Last reviewed May 2018 by David L. Horn, MD, FACP  Last Updated: 5/25/2018