Diphyllobothriasis (Dibothriocephalus latum)

MICROBIOLOGY

• The cestode (tapeworm) parasite, is found worldwide but concentrated in some endemic regions.
• Recent genus name change from Diphyllobothrium to Dibothriocephalus.
• The most important fish-borne zoonosis with a complex 3-host life cycle:
  
  • Eggs ingested by crustaceans and form the first larval stage → crustacean ingested by a freshwater fish where plerocercoid (second larval stage) develops → humans contract infection by eating raw or undercooked freshwater fish, and the parasite matures rapidly in the intestine [Figure 1].
  • Significant species are D. latum (U.S. Great Lakes region and Alaska, Scandinavia, Russia), D. nihonkaiense (Japan), D. pacificum (Pacific coast of South America), and D. dendriticum (Europe).
    • Cases also reported after eating imported fish.
    • At least 10 other species are occasionally reported in humans.