Broad Fish Tapeworm, Diphyllobothrium latum Adult broad fish tapeworms are found in the small intestine of fish-eating mammals such as bears, cats, and otters. They are huge worms, often more than several yards long. Several species of fish, primarily northern pike, carry these tapeworm larvae. If you eat improperly cooked fish infected with these larvae, they are likely to grow in your intestines too. Life Cycle: 1 The eggs pass in the droppings of the host mammal to water, where they hatch into free-swimming forms called coracidia. 2 Coracidia are eaten by microscopic crustaceans called copepods. Inside the copepods, they develop into larvae called procercoids. 3 When a fish eats an infected copepod, the procercoids move into the fish tissues. They develop into wormlike forms called plerocercoids. 4 When a mammal eats an infected fish, the plerocercoid attaches to the wall of its intestine and grows into a mature tapeworm. Effects on Fish: A broad fish tapeworm does not weaken a fish or stunt its growth. If a healthy northern pike, for example, eats an infected fish, the plerocercoid will migrate into the pike's flesh and encyst again. The plerocercoid will not develop into an adult tapeworm until a mammal eats the fish. Effects on People: Warning�if you eat an infected fish, tapeworms are likely to grow in your digestive tract. They are not only gross, but they also can cause a nutrient deficiency, especially a vitamin deficiency. People have died after getting this type of tapeworm from sources such as inadequately cooked or cold-processed pickled northern pike. To avoid this tapeworm, only eat thoroughly cooked fish. Cold-process pickling does not kill tapeworms or cysts! If you pickle fish, be sure to use heat in the processing.
