Tapeworms in Humans

Medically Reviewed by Sabrina Felson, MD on September 09, 2021
Written by Mary Anne Dunkin
3 min read

Tapeworms are flat, segmented worms that live in the intestines of some animals. Animals can become infected with these parasites when grazing in pastures or drinking contaminated water.

Eating undercooked meat from infected animals is the main cause of tapeworm infection in people. Although tapeworms in humans usually cause few symptoms and are easily treated, they can sometimes cause serious, life-threatening problems. That's why it's important to recognize the symptoms and know how to protect yourself and your family.

Six types of tapeworms are known to infect people. They are usually identified by the animals they come from -- for example, Taenia saginata from beef, Taenia solium from pork, and Diphyllobothrium latum from fish.

Tapeworms have a three-stage lifecycle: egg, an immature stage called a larva, and an adult stage at which the worm can produce more eggs. Because larvae can get into the muscles of their hosts, infection can occur when you eat raw or undercooked meat from an infected animal.

It is also possible to contract pork tapeworms from foods prepared by an infected person. Because tapeworm eggs are passed with bowel movements, a person who doesn't wash hands well after wiping and then prepares food can contaminate the food.

Sometimes tapeworms cause symptoms such as:

However, often tapeworms don't cause symptoms. The only sign of tapeworm infection may be segments of the worms, possibly moving, in a bowel movement.

In rare cases, tapeworms can lead to serious complications, including blocking the intestine, or smaller ducts in the intestine (like the bile duct or pancreatic duct).

If pork tapeworm larvae move out of the intestine, they can migrate to other parts of the body and cause damage to the liver, eyes, heart, and brain. These infections can be life-threatening. Seizures are the most common symptom of cysticercosis, the infection caused by the larvae of the pork tapeworm.

If you suspect you have tapeworms, see your doctor. Diagnosing a tapeworm infection may require a stool sample to identify the type of worm.

If worms are not detected in the stool, your doctor may order a blood test to check for antibodies produced to fight tapeworm infection. For serious cases, your doctor may use imaging tests such as computed tomography (CT) or magnetic resonance imaging (MRI) to check for tapeworm lesions or secondary swelling outside of the digestive tract.

The type and length of treatment may depend on the type of tapeworm you have. Tapeworms are usually treated with a medicine taken by mouth. The most commonly used medicine for tapeworms is praziquantel (Biltricide).

These medications paralyze the tapeworms, which let go of the intestine, dissolve, and pass from your body with bowel movements. If worms are large, you may have cramping when they pass. Your doctor will recheck stool samples at one and three months after you finish treatment. When tapeworms are confined to the intestines, appropriate treatment gets rid of them in more than 95% of people.

More serious complications of tapeworm infection are also treated with medications.

Tapeworms are uncommon in the U.S. today because of laws on feeding practices and inspection of the animals we use for food.

You can further reduce your risk of tapeworms by washing your hands before and after using the toilet and by following these food safety tips.

  • Avoid raw fish and meat.
  • Thoroughly cook meat to temperatures of at least 145 degrees Fahrenheit for whole cuts of meat and to at least 160 degrees F for ground meat and poultry. Then, allow the meat to rest for three minutes before carving or consuming; the heat continues killing pathogens during that time.
  • Freezing meat to -4 degrees F for at least 24 hours also kills tapeworm eggs.
  • When traveling in undeveloped countries, cook fruits and vegetables with boiled or chemically-treated water before eating.
  • Wash hands with soap and hot water before preparing or eating foods.