Helminth

Diphyllobothrium Latum

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Diphyllobothrium Latum, Fish Tapeworm, Broad Tapeworm, Diphyllobothriasis

  • See Also
  1. Helminth
  • Pathophysiology
  1. Fish Tapeworm (Diphyllobothrium Latum, Broad Tapeworm)
    1. Tapeworms (Cestodes) are Flatworms and lack their own intestinal tract
      1. Must obtain digested molecules from their environment (in this case from intestinal tract)
    2. Tapeworms are hermaphrodites, having both male and female organs within the same worm
      1. Single worm can produce fertilized eggs
    3. Tapeworms (Cestodes) are long and flat
      1. Tapewoms are composed in a chain of proglotitids (box-like segments)
      2. Tapeworm head (scolex) contains suckers, and for some species hooks
        1. Tapeworm larvae attach to the intestinal mucosa via suckers, and mature to adults
  2. Fish Tapeworm Infection
    1. Human ingestion of Tapeworm larvae in raw, freshwater fish (e.g. salmon, trout)
    2. Tapeworm larvae attach to the intestinal mucosa and mature to adult Tapeworms
    3. Fish Tapeworm infection is often asymptomatic, but abdominal cramping may occur
    4. Tapeworm may absorb significant amounts of Vitamin B12
      1. Risk of Vitamin B12 Deficiency (Pernicious Anemia)
    5. Fish Tapeworm attaches to the human intestinal tract and matures to a long adult (up to 45 meters)
      1. Adult Tapeworm sheds egg bundles within gravid proglottids (worm segments)
      2. Proglottids are passed into human stool
        1. Proglottids and eggs may be found in human stool (under stool sample microscopy)
    6. Fish Tapeworm has 2 intermediate hosts between human infections
      1. When Tapeworm eggs contaminate water, a motile larval Tapeworm (coracidia) emerges
      2. Small crustaceans (copepods in the genera Cyclops and Diaptomus) ingest the larval Tapeworms
      3. Freshwater fish ingest the infected crustaceans
      4. Humans become infected when they ingest raw freshwater fish
  • Labs
  1. Fecal Exam under light microscopy
    1. Proglottids and eggs may be identified
  2. Other labs to consider
    1. Hemoglobin
    2. Serum Vitamin B12
  • Management
  1. Personal hygiene
    1. Tapeworm eggs are infectious!
    2. Practice good hygiene and Hand Washing before, during and after treatment
  2. Praziquantel
    1. Dose: 5-10 mg/kg orally for 1 dose
    2. FDA approved for use in age >4 years, but has been used off-label for children age >=6 months
    3. Repeat fecal microscopy at 1 and 3 months after treatment to confirm resolution
  • Complications
  1. Vitamin B12 Deficiency
  • References
  1. Freedman (2024) Sanford Guide, Accessed on IOS 8/6/2025
  2. Gladwin, Trattler and Mahan (2014) Clinical Microbiology, Medmaster, Fl, p. 371