Ascariasis

What is ascariasis?

Ascariasis is an infection in your intestines caused by a roundworm called Ascaris lumbricoides (A. lumbricoides). Like other parasites, these worms use the body of a host (like a human) to mature into egg-laying adults. The more the worms thrive, the more harm they can cause the host.

A. lumbricoides is a kind of soil-transmitted helminth (STH). The worms living in someone’s gut lay eggs that exit through their stool (poop). If an infected person poops outside, the eggs transform into their infective form a few weeks later. Accidental ingestion of A. lumbricoides eggs in contaminated soil can create a new infection in that person. Eggs that contaminate food or water can also be accidentally ingested since they’re microscopic. Municipal water filtration treatment won’t allow eggs to get into normal tap water.

Although ascariasis infection is rare in the United States, it’s common in parts of the world with poor sanitation (for example, in places without widespread, easy access to toilets). In these areas, people are more likely to come into contact with contaminated soil, food or water.

What are the types of ascariasis?

The human roundworm (A. lumbricoides) is responsible for most cases of ascariasis. But the pig roundworm Ascaris suum (A. suum) can also cause human infection. You’re more at risk of an infection if you raise pigs or use pig manure for fertilizer.

How common is ascariasis?

Ascariasis is one of the most common human parasitic infections, affecting over 1 billion people worldwide. It’s the most common type of intestinal worm infection. Most infections affect children in tropical and subtropical parts of the world with poor sanitation.

What are the symptoms of ascariasis?

You may not have symptoms if you only have a few roundworms. Or, you may experience abdominal pain that comes and goes. The first sign of an infection may involve seeing a live worm in your vomit or poop. A. lumbricoides looks like common earthworms. The worms are about 6 to 13 inches long and are about as thick as a pencil.

If you do have symptoms, they vary based on where the worms are in your body. They’re in different places at different parts of their life cycle.

Infection in your lungs

Larvae (immature worms) can infect your lungs. At this early stage of the infection, you may have symptoms similar to pneumonia. Symptoms include:

• Wheezing.
• Cough.
• Shortness of breath.
• Fever.
• Hives (rare).

Symptoms are challenging to diagnose at this stage. They’re similar to symptoms of many other illnesses.

Infection in your intestines

Adult worms remain in your intestines. At this stage, you may experience mild or more intense abdominal symptoms depending on how many eggs you swallowed and where the adult worms end up. Symptoms include:

• Severe abdominal pain.
• Abdominal swelling.
• Nausea and vomiting.
• Occasional diarrhea.
• Loss of appetite.
• Unexplained weight loss.
• Restlessness.
• Trouble sleeping.

The more worms you have, the more severe your symptoms will be.

What causes ascariasis?

You can develop ascariasis if you ingest (swallow) the eggs of the human roundworm A. lumbricoides. These worms rely on your body as a hospitable climate that allows them to mature, mate and lay more eggs. The species relies on human hosts to complete its life cycle.

How is ascariasis transmitted?

Ascariasis spreads through hand-to-mouth contact — when someone touches and swallows fertilized A. lumbricoides eggs.

In places without adequate sanitation, people infected with ascariasis may poop outside. In some areas, people use human poop as fertilizer. Contaminated poop containing A. lumbricoides eggs can lie in fields, streets and yards without anyone knowing the eggs are there.

People may accidentally swallow the tiny eggs (too small to see with the naked eye) when they:

• Touch contaminated soil and then put their hands in or near their mouths.
• Eat fruits and vegetables grown in contaminated soil without washing with clean water, peeling and cooking the produce.
• Drink water contaminated with parasite eggs.

What is the life cycle of A. lumbricoides?

After you swallow the eggs, they pass into your intestines. There, they hatch into larvae and begin to travel through your body:

1. The larvae travel via your bloodstream or lymphatic system until they reach your lungs. They remain there for about two weeks.
2. They pass through the air sacs in your lungs and into your throat, where you re-swallow them.
3. The worms travel to your small intestine, where they mature into adults, mate and lay eggs. An adult female can lay more than 200,000 eggs daily.
4. The eggs exit your body through your poop.

The whole process of the complete life cycle can take two to three months.

After leaving your body through pooping, eggs take up to several weeks to become capable of infecting another person. The eggs can survive extreme weather and remain infective for up to 17 months.

If a new host ingests an egg during this time period, the cycle restarts in that person.

Who is at risk of ascariasis?

People at risk for ascariasis live in or visit places:

• With limited access to proper sanitation and hygiene (like toilets and clean water for handwashing).
• Where people use human poop (or pig poop with A. suum) as fertilizer.
• That are warm and humid, such as tropical and subtropical areas of Asia, sub-Saharan Africa and the Americas. Those weather conditions favor egg survival and transformation to an infective form.

Age is a risk factor, too. Children 8 years old or younger are more likely to get an infection. This is likely because it’s common for children to play outside in the dirt and then touch their mouths without washing their hands.

What are the complications of ascariasis?

Severe untreated infections can lead to complications, especially in children. Some are potentially fatal without treatment, but this is very rare.

• Bowel obstruction or a blockage in your ducts: Too many worms can partially or completely clog the passageways that move substances, like food and waste, through your digestive system. You may need emergency care to get rid of the blockage.
• Severe inflammation: Obstructions can lead to severe and even life-threatening inflammatory conditions. These include pancreatitis (inflammation in your pancreas), cholecystitis (inflammation in your gallbladder) and cholangitis (inflammation in your bile ducts).
• Malnutrition: An infection can prevent you from getting the nutrients you need. Children may experience growth problems because of nutritional deficiencies if they’re infected for a long time.

Diagnosis and treatment can prevent complications from ascariasis.

How is ascariasis diagnosed?

A healthcare provider can diagnose the infection using a stool sample once the worms have reached your intestines. They’ll check for eggs or worms inside your poop.

Ascariasis is harder to diagnose when the infection hasn’t spread beyond your lungs yet. If your provider suspects an infection, they may order a chest X-ray to check for changes that may indicate the larvae inside your lungs.

Other imaging tests — including ultrasounds, computed tomography (CT) scans and MRIs (magnetic resonance imaging scans) — can produce detailed images that show worms in places like your ducts. They can show how severe your infection is.

How is ascariasis treated?

Antiparasitic medications get rid of the infection by killing the adult worms. You’ll need to take your medicine for one to three days to kill all the adults. Most people start to feel symptom improvements fast, even before all the worms die. Treatment often results in pooping out the dead worms, which can be alarming.

Medicines include:

• Albendazole (Albenza^®).
• Ivermectin (Stromectol^®).
• Pyrantel pamoate (Pin-X^®), which may be a better option if you’re pregnant.

The medicines are best at killing the adult worms. The larvae aren’t as easily killed. You may need to take another round of the medicine in about one to three months to give the larvae time to mature into adults — so you can kill them, too.

Will I need surgery to treat ascariasis?

Although it’s rare, you may need surgery if there’s a complication, like a bowel obstruction. Your provider may need to remove the worms or repair damaged tissue.

Often, providers can make these repairs using the minimally invasive procedure endoscopic retrograde cholangiopancreatography (ERCP). It requires smaller incisions (cuts) and involves a faster healing time than traditional open surgery.

Can I prevent ascariasis?

If you live in or are traveling to an area where infection rates are high:

• Don’t touch potentially contaminated soil with your bare hands. This includes soil used to fertilize crops.
• Wash your hands with soap and water before preparing or eating food.
• Teach your children to wash their hands frequently.
• Wash, peel and/or cook any raw vegetables and fruits, especially if they grew in manure-fertilized soil.
• Don’t poop outdoors unless you’re using facilities that have proper sewage disposal.

What’s the outlook for people with ascariasis?

Ascariasis is highly treatable and doesn’t cause long-term problems if you take antiparasitic medications. Follow your provider’s instructions for taking your medicine. Take precautions to prevent reinfections.

What happens if ascariasis is left untreated?

The worms can live up to two years. When they die, you poop them out. Unless you ingest more eggs and restart the cycle, the infection is gone once the worms are gone.

Still, it’s a bad idea to “wait out” an ascariasis infection because of the complications it can cause. Also, if you live in an area where transmission is common, it’s easy to get reinfected.

See a healthcare provider if you or your child is experiencing symptoms of an infection or finds a worm in their poop that fits the description of A. lumbricoides.

What questions should I ask my healthcare provider?

Questions to ask include:

• Will I need tests to determine whether I have an infection?
• What type of treatment will I need?
• How long should I take medication?
• Will I have long-term health issues related to ascariasis?
• What can I do to keep from getting reinfected?

A note from Cleveland Clinic

Ascariasis is a common roundworm infection around the globe that’s preventable when communities have access to adequate sanitation facilities. If you live in or travel to an area with a high rate of infections, help protect yourself by washing your hands frequently. Rinse, peel and cook produce, and take care to properly prepare other food. If you do notice signs of ascariasis, like severe abdominal pain, see a provider. Antiparasitic medicines can kill the worms and clear the infection.