Taeniasis (Tapeworm Infection)

How tapeworm infection happens

The tapeworm life cycle involves two hosts:

1. An infected person passes tapeworm eggs and segments (proglottids) in their stool.
2. Cattle or pigs swallow the eggs from contaminated soil, water or feed.
3. The eggs hatch in the animal and form larval cysts (cysticerci) in its muscles.
4. A person eats raw or undercooked meat containing live cysts.
5. In the human intestine, the larva attaches to the wall with its head (scolex) and grows into an adult worm over about 2 to 3 months.

Adult beef tapeworms can reach 4 to 10 meters (13 to 33 feet) or more, and pork tapeworms 2 to 7 meters. They can live for years if untreated.

Beef vs pork tapeworm

A third species, Taenia asiatica, found in Asia, is caught from pork liver and organs and behaves like the beef tapeworm.

Symptoms

Many people have no symptoms. When present, they may include:

• Mild abdominal pain or discomfort
• Nausea, loss of appetite or increased appetite
• Weight loss
• Diarrhea or constipation
• Itching around the anus, from segments crawling out
• Noticing white or cream, flat, rectangular segments about half an inch (1 to 2 cm) long in stool, underwear or bedding

Rarely, a segment or worm blocks the appendix, bile duct or pancreatic duct, causing severe pain.

Cysticercosis: the pork tapeworm danger

If a person swallows eggs of T. solium, rather than the larval cysts in meat, the larvae can travel through the blood and form cysts in muscles, skin, eyes and the brain. This is cysticercosis. Cysts in the brain, called neurocysticercosis, are a leading cause of acquired epilepsy worldwide.

Eggs spread through food or water contaminated with stool from a person carrying the adult worm. Carriers can also infect themselves through unwashed hands. People who have never eaten pork can still get cysticercosis from a carrier who prepares their food.

Diagnosis

• Examining segments: a lab can identify the species from a passed segment by its internal structure.
• Stool tests: microscopy finds eggs, but beef and pork tapeworm eggs look identical. Several samples on different days may be needed because eggs are shed intermittently.
• Stool antigen tests and PCR, available in reference labs, can distinguish species.
• Blood count: sometimes shows mildly raised eosinophils.
• If pork tapeworm is found, the doctor may check for cysticercosis with blood antibody tests or a brain scan, especially if there are headaches or seizures.

Treatment

• Praziquantel or niclosamide, prescription anti-parasite medicines, usually given as a single dose, cure most infections. Niclosamide is not available in all countries.
• Stool is checked again at 1 and 3 months to confirm the worm is gone. Retreatment is occasionally needed.
• In people who may also have undiagnosed neurocysticercosis, praziquantel can inflame brain cysts and trigger seizures. Doctors consider this before treating pork tapeworm carriers.
• Household members of a pork tapeworm carrier may be screened.

Prevention

• Cook whole cuts of beef and pork to at least 145 °F (63 °C) measured with a food thermometer, then let rest for 3 minutes. Cook ground meat to 160 °F (71 °C).
• Avoid raw or undercooked meat dishes when traveling in high-risk areas.
• Freezing meat at -4 °F (-20 °C) for several days kills larval cysts. Smoking, salting and drying do not reliably kill them.
• Wash hands with soap and water after using the toilet and before handling food.
• Drink safe water and wash produce in areas with poor sanitation.
• Meat inspection and treating infected people and pigs reduce spread in communities.

Other tapeworms

Fish tapeworm (Diphyllobothrium) from raw freshwater or salmon-family fish can cause vitamin B12 deficiency. Dwarf tapeworm (Hymenolepis nana) spreads directly between people, mostly children. Pet tapeworms (Dipylidium) are caught by swallowing infected fleas. These are treated similarly but are not taeniasis.

Frequently asked questions

What are the symptoms of a tapeworm in humans?

Many people have none. Others notice mild belly pain, nausea, changes in appetite, weight loss, or itching around the anus. The most common sign is seeing white, flat, rice-like or rectangular segments in stool, underwear or bedding.

How do you get a tapeworm?

You get an intestinal tapeworm by eating raw or undercooked beef or pork containing tapeworm larvae. Swallowing pork tapeworm eggs from contaminated food, water or hands causes a different, more serious infection called cysticercosis.

How is a tapeworm infection treated?

A single dose of a prescription medicine, usually praziquantel or niclosamide, kills the adult worm in most cases. Stool is retested after 1 to 3 months to make sure the infection has cleared.

Can tapeworms spread from person to person?

The intestinal infection itself does not. But a person carrying a pork tapeworm sheds eggs that can infect others through contaminated food or hands, causing cysticercosis. Good handwashing and treatment of the carrier prevent this.

Can a tapeworm go to your brain?

The adult worm in the intestine cannot. But if you swallow pork tapeworm eggs, the larvae can travel to the brain and form cysts, called neurocysticercosis, which can cause seizures and headaches.