Tapeworms are a two stage parasite. The adult phase lives in the intestine of predators (like us). The larval phase stays dormant inside cysts embedded inside the meat of herbivores.

The adult tapeworm leeches nutrients from the intestine and lays tons of eggs, which go into the feces. These eggs then contaminate the environment and end up being eaten by herbivores. The eggs hatch inside their stomach and the larva embed themselves in the meat of the herbivore (and can even get in the brain). Finally, when the predator consumes uncooked meat contaminated with tapeworm larva, these larva further develop into adult tapeworms.

Each species of tapeworm is tuned to a specific species of herbivore. Cow tapeworm eggs often go right past us because they expect a tougher stomach than ours but pig tapeworm eggs can get confused because our stomach is similar to a pig's. Their larva can then embed into our meat, which is terrible for us but a dead end for the tapeworm (because we have no natural predators ourselves)

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To protect against intestinal tapeworms only eat well cooked meat. (For raw meats like sushi, deep freezing is also an option if done right)

Preventing tapeworm cysts is more about sanitation. Have clean water for drinking and irrigation and ensure that fruits and veggies are well cleaned. Good personal hygiene helps, in case you are already infected with an adult tapeworm (and therefore at risk of autoinfection).