Intestinal worms, also known as parasitic worms, are one of the main types of intestinal parasites in humans. They’re most commonly found in subtropical and tropical regions, but some types are found in the United States.

Most intestinal worm infections only cause mild illness and can be treated with medication. Read on to learn more about intestinal worms including signs, symptoms, and treatment.

Common symptoms of intestinal worms are:

A person with intestinal worms may also experience dysentery. Dysentery is when an intestinal infection causes diarrhea with blood and mucus in the stool. Intestinal worms can also cause a rash or itching around the rectum or vulva. In some cases, you will pass a worm in your stool during a bowel movement.

Some people may have intestinal worms for years without experiencing any symptoms.

Worms in your gut eventually pass through your digestive system and are excreted in your feces. Even if you don’t have any symptoms, you may find signs of worms in your stool.

Worms in human poop can take a number of appearances. For roundworms, you may find pieces of worms or large, live worms in your feces. For pinworms, you may see thin, white worms that appear like pieces of thread. Pinworms, which are about the length of a staple, are sometimes visible around the anal region at night, when females lay their eggs on the surrounding skin.

A doctor can analyze a sample of your stool in a lab for signs of worms or eggs that can confirm a diagnosis.

Common types of intestinal worms that can infect humans include:

  • flatworms, which include tapeworms and flukes
  • roundworms, which cause ascariasis, pinworm, and hookworm infections

Tapeworms

Humans get tapeworms by eating raw or uncooked pork or beef. Species that infect humans include:

  • Taenia saginata (beef tapeworm)
  • Taenia solium (pork tapeworm)
  • Taenia asiatica (Asian tapeworm)

It’s thought that fewer than 1,000 people in the United States are infected with tapeworms each year, although the exact number isn’t known. Tapeworms as long as 25 meters (82 feet) have been found in humans.

Flukes

More than 70 types of flukes can live in the human intestinal tract. They range from a fraction of an inch to several inches long. Humans can become infected by eating contaminated food or water. Flukes are most common in East and Southeast Asia.

Pinworms

It’s estimated that more than 1 billion people in the world are infected with pinworms, and they’re the most common type of worm that infects humans in North America. Children are most commonly infected. They’re easily passed between people living in close quarters.

Hookworms

It’s estimated that between 576 to 740 million people are infected with hookworms. They were once common in the United States, particularly in the Southeast, but they’ve become less common as living standards have improved. Most people infected with hookworms have no symptoms.

Ascariasis

Ascariasis is an infection of Ascaris lumbricoides and affects more than 800,000 million people in the world. It’s rare in the United States but may occur in the rural Southeast. Infection occurs from contaminated food or water. Adult worms can grow more than a foot long. Usually, they don’t cause symptoms.

Here’s an example of what intestinal worms look like:

One way to become infected with intestinal worms is by eating undercooked meat from an infected animal, such as a cow, pig, or fish. Other possible causes leading to intestinal worm infection include:

Once you’ve consumed the contaminated substance, the parasite travels into your intestines. Then they reproduce and grow in the intestine. Once they reproduce and become larger in amount and size, symptoms may appear.

Children are particularly susceptible to intestinal worms because they often play in environments with contaminated soil, such as sandboxes and school playgrounds. Older adults are also at increased risk due to weakened immune systems.

According to the World Health Organization (WHO), an estimated 24 percent of the world’s population is infected with soil-transmitted worms. Infections are most common in tropical and subtropical regions, in particular, Sub-Saharan Africa, the Americas, China, and East Asia.

People living in and visiting developing countries are at the highest risk due to drinking water from contaminated sources and decreased sanitation levels.

Intestinal worms increase your risk for anemia and intestinal blockages, as well as malnutrition. Complications occur more frequently in older adults and in people who have suppressed immune systems, such as people with HIV/AIDS infection.

Intestinal worm infections can pose a higher risk if you’re pregnant. If you’re pregnant and are found to have an intestinal worm infection, your doctor will determine which antiparasitic medication therapy is safe to take during pregnancy and will monitor you closely while you are treated during pregnancy.

Most types of worms that infect humans only cause mild symptoms, but it’s still important to contact a doctor if you suspect a worm infection so you can get treated early. Medication is often effective at getting rid of worms.

It’s a good idea to see your doctor if you:

  • have blood or pus in your stool
  • are vomiting daily or frequently
  • have an elevated body temperature
  • are extremely fatigued and dehydrated
  • are losing weight for no obvious reason
  • feel sick, have diarrhea, or have stomach pain for more than 2 weeks
  • have a red and itching rash on your skin shaped like a worm

If you have any of the above signs, and especially if you have traveled out of the country recently, you should make an appointment with a doctor. A doctor may then examine your stool. It may take several stool samples to confirm the parasite’s presence.

Another test is the “Scotch tape” test, which involves applying tape to the anus several times in order to retrieve pinworm eggs, which can be identified under a microscope.

If worms or eggs are not detected, a doctor may carry out a blood test to look for antibodies that your body produces when it’s infected with a parasite. However, only some parasites are detectable with blood tests.

Additionally, a doctor may take an X-ray or use imaging tests such as computed tomography (CT) or magnetic resonance imaging (MRI), depending on the extent or locations of the condition suspected.

Some types of intestinal worms, such as tapeworms, may disappear on their own if you have a strong immune system and healthy diet and lifestyle. However, depending on the type of intestinal worm infection, you may require treatment with an antiparasitic medication.

Your treatment plan will be determined based on the type of intestinal worm you have and your symptoms.

Tapeworm infections are usually treated with an oral medication, such as praziquantel (Biltricide), which:

  • paralyzes adult tapeworms
  • causes the tapeworms to detach from the gut
  • dissolve
  • pass out of your body through your stool

Common treatments for a roundworm infection include mebendazole (Vermox, Emverm) and albendazole (Albenza).

Medications for intestinal worms are usually taken for 1 to 3 days. Symptoms typically begin to improve within a few weeks. Your doctor will most likely take and analyze another stool sample after treatment is complete to see if the worms have disappeared.

To prevent intestinal worms, regularly wash your hands with soap and hot water before and after using the toilet and before preparing or eating foods.

You should also practice food safety:

  • avoid raw fish and meat
  • thoroughly cook meat to temperatures of at least 145°F (62.8°C) for whole cuts of meat and 160°F (71°C) for ground meat and poultry
  • let cooked meat rest for 3 minutes before carving or consuming
  • freeze fish or meat to –4°F (–20°C) for at least 24 hours
  • wash, peel, or cook all raw fruits and vegetables
  • wash or reheat any food that falls on the floor

If you’re visiting developing countries, cook fruits and vegetables with boiled or purified water before eating, and avoid contact with soil that may be contaminated with human feces.