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Causes
By Mayo Clinic staff
In humans, tapeworm disease is most commonly caused by one of several tapeworm species: the pork tapeworm (Taenia solium), beef tapeworm (Taenia saginata), dwarf tapeworm (Hymenolepis nana), and fish tapeworm (Diphyllobothrium latum) from raw freshwater fish.
You usually get tapeworm infection by ingesting tapeworm eggs or larvae.
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Ingestion of eggs. Tapeworm eggs are generally ingested through food, water or soil contaminated with human or animal (host) feces.
For example, if a pig is infected with a tapeworm, it may pass eggs or segments (proglottids) of the adult tapeworm through its feces into soil. Each segment contains thousands of microscopic tapeworm eggs. You can then ingest these eggs by eating food contaminated with the feces. Once you consume the eggs, they develop into larvae, which can migrate out of your intestines and form cysts in other tissues such as your lungs or liver. This type of infection is not common with beef or fish tapeworms, but can occur with the pork tapeworm — called cysticercosis — and can also occur with dog and sheep tapeworms — called echinococcosis.
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Ingestion of larvae cysts in meat or muscle tissue. You can also get tapeworm infection by eating raw or undercooked meat from an animal or a fish that has the larval form of the tapeworm (cysts) in its muscle tissue. Once you ingest them, the larvae then develop into adult tapeworms in your intestines.
Adult tapeworms can measure up to 50 feet long and can survive as long as 20 years. Some tapeworms attach themselves to the walls of the intestine, where they cause irritation or mild inflammation, while others may pass through to your stool and exit your body.
Unlike other tapeworms, the dwarf tapeworm can complete its entire life cycle — egg to larva to adult tapeworm — in one host. This is the most common tapeworm infection in the world and can be transmitted between humans.
While being treated for certain tapeworm infections, you can reinfect yourself by ingesting tapeworm eggs shed by the adult worm into your stool. That's why you should take care to wash your hands after using the toilet.
