Fish should therefore not be eaten raw or undercooked specially fresh-water pike. It causes the dwarf tapeworm infection. It is a very small tapeworm which does not need an intermediate host. The ova may remain in the intestine and develop to the larval form and finally to the adult tapeworm. In this way heavy infestation can take place.
Contamination takes place through fecal contaminated food and hands.
Mice and rats may also bear Hymenolepis nana. It causes the hydatid cyst. The adult stage lives in dog. The ova of the dog feces when ingested by sheep, hogs or cattle develops as larvae in the liver. If dogs feed from these animals during slaughter the ingested ova develop to adult tapeworms.