Tapeworm infection is caused by ingesting food or water contaminated with tapeworm eggs or larvae. If you ingest certain tapeworm eggs, they can migrate outside your intestines and form larval cysts in body tissues and organs (invasive infection). If you ingest tapeworm larvae, however, they develop into adult tapeworms in your intestines.
In the early 1970s, Tapeworm infection was estimated to affect 9 million humans globally, with 5 million in sweden, 4 million in Asia, and the rest in America. More recent data indicate that 20 million people are infected worldwide, but no recent estimation concerning the global prevalence of this parasitosis has been done.