Diphyllobothrium is a genus of the class Cestoda (tapeworm) of the phylum Platyhelminthes. It includes the medically-important tapeworm D. latum that causes diphyllobothriasis in a human host. Infection in humans is usually by eating uncooked fish. The larval stage is known as sparganum. It occurs in Scandinavia, western Russia, and the Baltics. It is regarded as the longest human tapeworm, reaching about ten meters long.
Other species are D. dendriticum (commonly known as the salmon tapemorm), D. pacificum, D. cordatum, D. ursi, D. lanceolatum, D. dalliae, D. yonagoensis, and D. nihonkaiense. Nevertheless, these species are not as frequently found in human hosts unlike D. latum.
The adult worm has a similar body plan to other cestodes. There are three main parts: the head or scolex, the neck, and the proglottids. The scolex of Diphyllobothrium has a bothrium (a slit-like groove) that the worm uses to attach to the host intestine. The neck is the proliferative region that gives rise to new proglottids. The proglottids contain the reproductive organs (for sexual reproduction).
- Kingdom: Animalia
- Phylum: Platyhelminthes
- Class: Cestoda
- Subclass: Eucestoda
- Order: Pseudophyllidea
- Family: Diphyllobothriidae
- Genus: Diphyllobothrium
- Species: D. latum, D. pacificum, D. cordatum, D. ursi, D. dendriticum, D. lanceolatum, D. dalliae, D. yonagoensis, D. nihonkaiense