Cordicephalus Wardle, McLeod & Stewart, 1947 Diphyllobothrium is a genus of tapeworms which can cause diphyllobothriasis in humans through consumption of raw or undercooked fish.

[1] Other members of the genus Diphyllobothrium include D. dendriticum (the salmon tapeworm), which has a much larger range (the whole northern hemisphere), D. pacificum, D. cordatum, D. ursi, D. lanceolatum, D. dalliae, and D. yonagoensis, all of which infect humans only infrequently.

[3] The adult worm is composed of three fairly distinct morphological segments: the scolex (head), the neck, and the lower body.

[5] Adult tapeworms may infect humans, canids, felines, bears, pinnipeds, and mustelids, though the accuracy of the records for some of the nonhuman species is disputed.

After ingestion by a suitable freshwater crustacean such as a copepod (the first intermediate host), the coracidia develop into procercoid larvae.

[6] Because humans do not generally eat undercooked minnows and similar small freshwater fish, these do not represent an important source of infection.

One or several of the tape-like proglottid segments (hence the name tapeworm) regularly detach from the main body of the worm and release immature eggs in freshwater to start the cycle over again.

[11][12] The worm absorbs around 80% of dietary B12 and prolonged infection can also cause abdominal pain, mechanical obstruction, and symptoms of iron deficiency anemia.