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.