What is ascariasis?

Ascariasis is an infection of the small intestine caused by Ascaris lumbricoides (A. lumbricoides), which is a species of roundworm.

Roundworms are a type of parasitic worm. Infections caused by roundworms are fairly common. Ascariasis is the most common roundworm infection. About 10 percent of the developing world is infected with intestinal worms, according to the World Health Organization (WHO). However, infections with parasitic worms are not as common in the United States, according to the Centers for Disease Control and Prevention (CDC).

Learn more: Parasitic infections »

Ascariasis is most common in places without modern sanitation. People get it through unsafe food and water. The infection usually causes no symptoms, but higher numbers of roundworms (heavier infestations) can lead to problems in the lungs or intestines.

What causes an ascariasis infection?

You can become infected with ascariasis after accidentally ingesting the eggs of the A. lumbricoides roundworm. The eggs can be found in soil contaminated by human feces or uncooked food contaminated by soil that contains roundworm eggs. Children often become infected when they put their hands in their mouths after playing in contaminated soil, according to WHO. Ascariasis can also be passed directly from person-to-person.

After ingestion, the A. lumbricoides roundworm reproduces inside your intestine. The worm goes through several stages:

  • Swallowed eggs first hatch in the intestine.
  • The larvae then move through your bloodstream to your lungs.
  • After maturing, the roundworms leave your lungs and travel to your throat.
  • You’ll either cough up or swallow the roundworms in your throat. The worms that are swallowed will travel back to your intestine.
  • Once they’re back in your intestine, the worms will mate and lay more eggs.
  • The cycle continues. Some eggs are excreted through your feces. Other eggs hatch and return to the lungs.
Who is at risk for ascariasis?

The roundworm is found worldwide, but it’s more frequently found in tropical and subtropical regions, including Latin America and sub-Saharan Africa. It’s also more common in areas where sanitation is poor.

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 environment where dirt might be ingested

You can limit your exposure to roundworms by avoiding unsafe food and water. Keeping your immediate environment clean also helps. This includes laundering clothing exposed to unsanitary conditions and cleaning cooking surfaces well.

You should make sure to take precautions if you’re visiting a remote area. It’s important to:

  • Always wash your hands with soap and water before eating or preparing food.
  • Boil or filter your water.
  • Inspect food preparation facilities.
  • Avoid unclean common areas for bathing.
  • Peel or cook unwashed vegetables and fruit in regions that lack sanitation infrastructure or that use human feces for fertilizer.

Children who are 3 to 8 years old are most likely to be infected because of their contact with soil while playing.

Read more: Hygiene habits for kids »

What are the symptoms of ascariasis?

People with ascariasis often have no symptoms. Symptoms become more noticeable when the roundworm infestation grows.

Roundworms in your lungs can cause:

Roundworms in your intestines can cause:

Some people with a large infestation may have 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 don’t receive prompt treatment.

What are the complications of ascariasis?

Most cases of ascariasis are mild and don’t cause major problems. However, heavy infestations can spread to other parts of the body and lead to dangerous complications. They can include:

  • Intestinal blockage occurs when a mass of worms blocks your intestines causing severe pain and vomiting. Intestinal blockage is considered a medical emergency and requires treatment right away.
  • Duct blockages occur when the worms block the small passageways to your liver or pancreas.
  • Infections that lead to loss of appetite and poor absorption of nutrients puts children at risk of not getting enough nutrients, which can affect their growth.

Children are more likely to have gastrointestinal complications because their small intestines increase their chances of having an intestinal blockage.

How is ascariasis diagnosed?

Doctors generally make the diagnosis by examining a stool sample for parasites and ova (eggs). If your doctor suspects you have ascariasis, he or she will ask for a stool sample from you.

If you’re diagnosed with ascariasis, you may need more tests, such as one of these imaging tests:

Imaging tests can show:

  • how many worms have grown to maturity
  • where major groups of worms are inside the body

To evaluate your risk for complications, it’s important for your doctor to determine how long you’ve been infected.

How is ascariasis treated?

Doctors usually treat roundworm with antiparasitic drugs. Medications most commonly used include:

  • albendazole (Albenza)
  • ivermectin (Stromectol)
  • mebendazole (Vermox)

If you have an advanced case, you may need other treatment. Your doctor may recommend surgery to control a larger infestation. You’ll need surgery if the roundworms are completely blocking your intestines.

What is the long-term outlook for an ascariasis infection?

Many people recover from ascariasis with minimal treatment. Symptoms may go away even before all the worms are gone.

However, ascariasis can cause complications when there are large infestations. If you think you’ve been infected with roundworms, be sure to see your doctor.

The best way to avoid ascariasis is by:

  • Practicing good hygiene. That means always wash your hands with soap and water before eating or handling food, and after using the bathroom. Teach your children to do the same.
  • Dining only at reputable places.
  • Drinking only bottled water and avoiding raw fruits and vegetables unless you’re able to wash and peel them yourself when you’re in places without modern sanitation.