Ascariasis (as-kuh-RIE-uh-sis) is a type of roundworm infection. These worms are parasites that use your body as a host to mature from larvae or eggs to adult worms and reproduce. Adult worms can be more than a foot (30 centimeters) long.

Ascariasis is one of the most common human worm infections worldwide, although it's uncommon in the United States. Because most people have such mild cases of ascariasis, they have no symptoms. But when your body is infested with hundreds of worms, serious symptoms and complications can occur.

Ascariasis occurs most often in young children and is most prevalent in tropical and subtropical regions of the world — especially in areas where sanitation and hygiene are poor. In the United States, ascariasis is most likely to occur in rural areas of the Southeast.

Symptoms Causes Risk factors Complications Prevention

Most people infected with ascariasis have no symptoms. Moderate to heavy infestations cause symptoms that may vary, depending on which part of your body is affected.

In the lungs

After you ingest the microscopic ascariasis eggs, they hatch in your small intestine and the larvae migrate through your bloodstream or lymphatic system into your lungs. At this stage, you may experience signs and symptoms similar to asthma or pneumonia, including:

  • Persistent cough
  • Shortness of breath
  • Wheezing

After spending six to 10 days in the lungs, the larvae travel to your throat, where you cough them up and then swallow them.

In the intestines

The larvae mature into adult worms in your small intestine, and the adult worms typically live in the intestines until they die. In mild or moderate ascariasis, the intestinal infestation can cause:

  • Vague abdominal pain
  • Nausea and vomiting
  • Diarrhea or bloody stools

If you have a heavy intestinal infestation — a large number of worms — you may experience:

  • Severe abdominal pain
  • Fatigue
  • Vomiting
  • Weight loss
  • A worm in vomit or stool

When to see a doctor

Consult your doctor if you have persistent abdominal pain, diarrhea or nausea.

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