Written by Seth Stoltzfus and Elizabeth Boskey, PhD | Published on July 25, 2012
Medically Reviewed by George Krucik, MD


Ascariasis is an infection caused by Ascaris lumbricoides, which is one species of roundworm.

Infections caused by roundworms—which are a type of parasitic worm that can be as small as one millimeter or as long as a one meter—are relatively common. Ascariasis is the most common roundworm infection. According to the World Health Organization, as many as one billion people are infected by Ascaris lumbricoides worldwide.

Ascariasis is most common in places without modern sanitation. It is transmitted through unsafe food and water. Municipally treated drinking water decreases the frequency of the disease.

What Causes Ascariasis Infection?

The Ascaris lumbricoides roundworm reproduces inside the intestine. The worm goes through several stages:

  • Swallowed eggs first hatch in the intestine.
  • The larvae then move through the bloodstream to the lungs.
  • After maturing, the roundworms leave the lungs and return to the stomach and small intestine.
  • There they lay eggs.
  • The cycle continues. Some eggs are excreted through the feces. Other eggs hatch and return to the lungs.

Ascariasis occurs when the eggs that have been excreted in human feces infect a new person.

Infection can happen when feces contaminate water or food. Ascariasis can also be passed directly from person to person.

Who Is at Risk for Ascariasis?

Environmental risk factors for ascariasis include:

  • lack of modern hygiene and sanitation infrastructure
  • use of human feces for fertilizer
  • living in or visiting a warm climate
  • exposure to an outdoor environment where dirt might be ingested (children)

Exposure to roundworm can be limited by avoiding unsafe food and water. Keeping your immediate environment clean also helps. This includes laundering clothing exposed to unsanitary conditions and cleaning all surfaces well.

If you’re visiting a remote area, make sure to take precautions:

  • boil or filter your water
  • inspect food preparation facilities
  • avoid unclean common areas for bathing

According to the WHO, infection is most common among children three to eight years old.

What Are the Symptoms of Ascariasis?

Ascariasis produces different symptoms in its various stages. Your condition depends on where you have eggs or larvae in your body.

Symptoms associated with roundworms in the lungs include:

  • coughing or gagging
  • vomiting roundworms
  • wheezing or shortness of breath

Roundworms in your intestines cause the following symptoms:

  • nausea
  • vomiting
  • irregular stools
  • stomach or abdominal pain
  • weight loss

Some people with a large infestation may experience other symptoms, such as fatigue and fever. A major infestation can cause extreme discomfort. You may have all or many of the above symptoms if you do not receive prompt treatment.

Ascariasis can also cause complications. These include bowel obstruction and pancreatitis. Complications occur when worms gather in other areas of the body. They may cause blockages, inflammation, or other damage.

How Is Ascariasis Diagnosed?

Not all people with ascariasis have symptoms. Blood and stool samples are a far more accurate way of detecting roundworms. Abdominal X-rays can also be used to diagnose the disease.

If your doctor diagnosis roundworm, he may recommend additional tests. Advanced imaging can show:

  • how many worms have grown to maturity
  • where major groups of worms are located
  • whether worms are in the areas around your internal organs

Such tests might involve CT scans, ultrasound, or MRI. The extent of your infestation can also be determined by endoscopy. This involves placing a small camera inside the body.

It is important for your doctor to determine how long you have had this condition. That way he can evaluate your risk of complications.

How Is Ascariasis Treated?

Roundworm is usually treated with anti-parasitic drugs. Medications used for treatment include:

  • albendazole
  • ivermectin
  • mebendazole

In advanced cases other treatment may be needed. Surgery may be used to control a larger infestation.

What is the Long-Term Outlook for an Ascariasis Infection?

Many patients recover from ascariasis with minimal to no treatment. Symptoms may go away even if you still have some worms.

However, ascariasis can cause complications when worms are present in certain organs. If you have symptoms, it is a good idea to seek treatment.

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