Head of a pork tapeworm. Left image is magnified 30 times, right one is magnified about 55 times.

Tapeworms are the class Cestoda of segmented flatworms (Platyhelminthes).They are parasitic, which means that they need another larger creature as a host. Tapeworms live inside the intestines of vertebrate animals. This includes humans. When a vertebrate has a tapeworm, they may lose weight and become weaker.