Tapeworms are parasites that can live in the intestines of humans and other animals. They are flat, segmented worms that grow to different lengths depending on their host organisms, and the amount of time they go undetected. Their three-stage lifecycle includes an egg, a larva, and an adult stage. Once they reach the adult stage, they are capable of producing eggs thus perpetuating the cycle. Humans can be infected by all three stages of tapeworm development. It is possible for animals to become infected by tapeworms by drinking infested water or when grazing in fields where tapeworm eggs thrive. Many cases of tapeworms in humans come from eating undercooked meat from animals that contain the parasites. Six different types of tapeworms can infect humans. Their names are derived from the animals that host them; examples include Taenia siginata from beef and Taenia solium from pork.