Where do tapeworms come from?
Primarily, tapeworms come from fleas.
Since fleas are the intermediate host of Dipylidium caninum, the most common species of tapeworm, pet owners should be on the lookout for flea infestations.
Dipylidium caninum, as an adult tapeworm, attaches to the walls of the small intestine. As the tapeworm matures, the egg-engorged segments — proglottids — break off. [...]