Tapeworms are large, flat parasitic worms that live in the intestinal tracts of some animals. They are passed to humans who consume foods or water contaminated with tapeworm eggs or larvae.

Six types of tapeworms are known to infect humans, usually identified by their source of infestation: beef, pork, fish, dog, rodent, and dwarf, which is named because it is small.

Digestive Pathway
Digestive pathway
Tapeworms enter the human body with contaminated food or water and remain in the intestines.
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Tapeworm infection in people usually results from eating undercooked foods from infected animals. Pigs or cattle, for example, become infected when grazing in pastures or drinking contaminated water. People can also become infected by eating contaminated fish that is raw or undercooked.

The parasites mature in the animal’s intestines to pea-shaped larvae. They spread to the animal's blood and muscles. They are then transmitted to people who eat the contaminated food. This method is more common with beef or fish.

Tapeworms can also be passed by hand-to-mouth contact if you touch a contaminated surface and then touch your mouth. This method is more common with pork.