Cestodes. S. mansoni, S. ranarum, S. mansonoides and S. erinacei, Sparganum proliferum
Eating raw frogs and snakes or drinking contaminated water. The normal host is the dog and cat. Can live up to 20 years in people.
Mass effect in whatever tissue it settles in.
To quote the CDC "Surgical removal is the treatment of choice for sparganosis. Generally, treatment with mebendazole, albendazole, or praziquantel is not effective to treat infection with these larvae. In rare cases of proliferative sparganosis, prolonged treatment with mebendazole and praziquantel have been used in addition to surgical removal with mixed success."