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BackFact Sheet

What is an ascaris infection?

An ascarid is a worm that lives in the small intestine. Infection with ascarids is called ascariasis (ass-kuh-rye-uh-sis). Adult female worms can grow over 12 inches in length, adult males are smaller.

How common is ascariasis?

Ascariasis is the most common human worm infection. Infection occurs worldwide and is most common in tropical and subtropical areas where sanitation and hygiene are poor. Children are infected more often than adults. In the United States, infection is rare, but most common in rural areas of the southeast.

What are the signs and symptoms of an ascaris infection?

Most people have no symptoms. If you are heavily infected, you may have abdominal pain. Sometimes, while the immature worms migrate through the lungs, you may cough and have difficulty breathing. If you have a very heavy worm infection, your intestines may become blocked.

How is an ascaris infection spread?

Ascarid eggs are found in the soil. Infection occurs when a person accidently ingests (swallows) infective ascarid eggs. Once in the stomach, larvae (immature worms) hatch from the eggs. The larvae are carried through the lungs then to the throat where they are then swallowed. Once swallowed, they reach the intestines and develop into adult worms. Adult female worms lay eggs that are then passed in feces; this cycle will take between 2-3 months.

Pigs can be infected with ascarids. Occasionally, a pig ascarid infection can be spread to humans; this occurs when infective eggs, found in the soil and manure, are ingested. Infection is more likely if pig feces is used as fertilizer in the garden; crops then become contaminated with ascarid eggs.

How can I get ascariasis?

You or your children can become infected after touching your mouth with your hands contaminated with eggs from soil or other contaminated surfaces.

What should I do if I think I have ascariasis?

See your health care provider.

How is diagnosis of ascaris made?

Your health care provider will ask you to provide stool samples for testing. Some people notice infection when a worm is passed in stool or is coughed up. If this happens, bring in the worm specimen to your health care provider for diagnosis. There is no blood test used to diagnose an ascarid infection.

What is the treatment for ascariasis?

In the United States, ascaris infections are generally treated for 1-3 days with medication prescribed by your health care provider. The drugs are effective and appear to have few side-effects. Your health care provider will likely request additional stool exams 1 to 2 weeks after therapy; if the infection is still present, treatment will be repeated.

I am pregnant and have just been diagnosed with ascariasis. Can I be treated?

Infection with ascarid worms is generally light and is not considered an emergency. Unless your infection is heavy, and your health may be at risk, treatment is generally postponed until after delivery of the baby.

How can I prevent infection with ascarids?

  • Avoid contacting soil that may be contaminated with human feces.
  • Do not defecate outdoors.
  • Dispose of diapers properly.
  • Wash hands with soap and water before handling food.
  • When traveling to countries where sanitation and hygiene are poor, avoid water or food that may be contaminated.
  • Wash, peel or cook all raw vegetables and fruits before eating.

Should I be concerned about spreading infection to the rest of my household?

No. Infection is not spread from person to person.

For more information:

Sarinas PS, Chitkara RK. Ascariasis and hookworm. Semin Respir Infect 1997 Jun;12(2):130-7


This fact sheet is for information only and is not meant to be used for self-diagnosis or as a substitute for consultation with a health care provider. If you have any questions about the disease described above or think that you may have a parasitic infection, consult a health care provider.

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