What Is Ascariasis?

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Ascariasis is a parasitic infection of the intestine caused by the roundworm Ascaris lumbricoides. Millions of people are infected with the worms, but often they do not have symptoms and will not have severe complications. Ascariasis is common in people who do not have access to clean water or proper sanitation. 

This article discusses the symptoms, causes, and complications of ascariasis as well as how to treat and prevent it.

Male and female Ascaris worms (Ascaris lumbricoides)

Dr_Microbe / Getty Images

Ascariasis Symptoms

Ascaris lumbricoides is a roundworm that can cause a parasitic infection in the intestine. The disease process and associated symptoms are called ascariasis. 

Often, people do not have any symptoms. When symptoms do occur, it generally means the person is infected with a large number of worms.

Millions of people worldwide are infected with the parasite, but it is uncommon in the U.S.

Symptoms of ascariasis are often not very severe and include:

  • Abdominal discomfort
  • Loss of appetite
  • Nausea or vomiting
  • Diarrhea
  • Weight loss
  • Transient respiratory symptoms (as the immature worms migrate through the body to the lungs)

How Common Is Ascariasis?

The Centers for Disease Control and Prevention (CDC) estimate that approximately 800 million to 1.2 billion people are infected with Ascaris lumbricoides. The highest rates of infection are in Asia.

Ascariasis Causes

People become infected with Ascaris lumbricoides by accidentally ingesting eggs found in human feces.

When a person with the infection defecates outside, the eggs are deposited in the soil. The worm eggs live in the ground in places that do not have access to proper sanitation and where people do not practice good hygiene. A person can ingest the worm eggs if:

  • Their hands or fingers touch the dirt
  • They eat unwashed fruits or vegetables that grow in the contaminated soil
  • They drink contaminated water

After a person has ingested worm eggs, they hatch, and the larvae mature in a few days. Then, they migrate throughout the rest of the intestine. Sometimes, they migrate outside the intestine and go to other organ systems like the liver, heart, and lungs.

When the worm larvae are in the lungs, people can experience mild respiratory symptoms such as:

These respiratory symptoms are usually mild and short-lived.

While coughing, small worms are swallowed back into the intestine, where they grow to become adult worms. The cycle then continues with worms laying eggs in the intestine, which are then excreted into areas where the eggs can be transmitted to another person.

Parasitic infections like ascariasis decreased significantly in the United States by introducing modern sanitation and waste treatment. However, the infection still occurs among people who travel to areas with high disease rates and lack of sanitation.

Other Worms That Lead to Ascariasis

Humans can also be infected with a roundworm from pigs called Ascaris suum. The symptoms are the same. It is unknown how many people worldwide are infected with this parasite, but it is not as common as infection with Ascaris lumbricoides.

Ascariasis Treatment

Several antiparasitic agents are effective against ascariasis. However, taking these medications does not prevent reinfection and, according to several studies, reinfection with the parasite happens quickly after treatment. This is why it's essential to practice proper hygiene and environmental sanitation.

The drugs of choice to treat ascariasis include:

  • Albendazole
  • Mebendazole

These drugs are very effective with very few side effects. They only need to be taken for one to three days. In fact, a single dose of albendazole is frequently effective in curing ascariasis.

Ivermectin is an alternative treatment option recommended by the CDC.


The most effective way to reduce the transmission of Ascaris lumbricoides is to implement adequate sanitation and clean water systems.

In places where people are without such systems, it's vital to:

  • Not defecate outdoors
  • Wash hands with clean soap and water
  • Wash and peel fruits and vegetables

Finally, mass pharmacologic treatment with medications for people at risk for ascariasis or who live in areas with high infection rates can reduce the overall spread of the disease and reinfection after treatment.


It takes several weeks for adult worms to grow to the point that they can be visible in the stool. It is during this later stage of the disease that complications can develop.

The most common complication is a heavy load of parasites that obstructs the intestine. Sometimes, the obstruction can specifically affect the appendix leading to appendicitis.

The worms can also migrate to other organ systems and lead to inflammation of the liver, pancreas, and gallbladder. The diseases that people can develop include:

Ascariasis in children is also associated with malnutrition, slow growth, and impaired thinking and verbal abilities. When children have many parasites in the intestine, absorption of proper vitamins and nutrients cannot happen. 

Parasitic infections like ascariasis are a common cause of growth impairment and low red blood cell counts in children.

When to Be Concerned About Ascariasis

Ascariasis is not very common in the United States. But, if you have traveled to an area where the disease is common, have potentially come into contact with contaminated soil and water, and see worms in your stool, see your healthcare provider.


Ascariasis is a parasitic infection of the intestines that affects millions worldwide. It is caused by a parasite called Ascaris lumbricoides that is found in the soil. The organism is transmitted from one person to another by ingesting contaminated food and water.

Most people don’t have any symptoms, but the worms can lead to complications such as small bowel obstruction. Treatment involves antiparasitic agents such as albendazole. The best way to prevent the illness is by implementing effective sanitation and clean water systems and encouraging proper hygiene.

A Word From Verywell

Millions of people are infected with Ascaris lumbricoides. Still, it is not as common in places with clean water and sanitation. If you live or have traveled to an area without proper sanitation and see worms in your stool, consider ascariasis. Fortunately, it is easily treated.

Frequently Asked Questions

  • Can ascariasis lead to death?

    Complications from ascariasis lead to death in about 2,000 people. However, most people with ascariasis do not develop any symptoms, let alone complications that lead to death.

  • What happens if ascariasis is left untreated?

    If ascariasis is left untreated, people can develop a high load of worms in the intestine, leading to complications such as bowel obstruction, spreading to other organ systems, and malnutrition.

  • Is ascariasis contagious?

    Ascariasis cannot be transmitted by coughing, touch, or bodily fluids. The parasite is transmitted through the fecal-oral route when someone ingests contaminated soil, foods, or water.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Christine Zink, MD
Dr. Christine Zink, MD, is a board-certified emergency medicine with expertise in the wilderness and global medicine. She completed her medical training at Weill Cornell Medical College and residency in emergency medicine at New York-Presbyterian Hospital. She utilizes 15-years of clinical experience in her medical writing.