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For further information, see CMDT Part 35-18: Noninvasive Cestode Infections

Key Features

Essentials of Diagnosis

  • Infections are generally asymptomatic

  • Nonspecific gastrointestinal symptoms, including diarrhea, may occur

  • Prolonged heavy infection can lead to megaloblastic anemia and neuropathy from vitamin B12 deficiency

General Considerations

  • Six tapeworms infect humans frequently

  • The large tapeworms are

    • Taenia saginata (the beef tapeworm, up to 25 m in length)

    • Taenia solium (the pork tapeworm, 7 m)

    • Diphyllobothrium latum (the fish tapeworm, 10 m)

  • The small tapeworms are

    • Hymenolepis nana (the dwarf tapeworm, 25–40 mm)

    • Hymenolepis diminuta (the rodent tapeworm, 20–60 cm)

    • Dipylidium caninum (the dog tapeworm, 10–70 cm)

  • Eggs passed in human feces that reach fresh water are taken up first by crustaceans, which in turn are eaten by fish, both of which are intermediate hosts

  • Human infection results from eating undercooked freshwater fish

  • Infection with multiple worms over many years can occur

  • Nonhuman reservoir hosts include dogs, bears, and other fish-eating mammals

Demographics

  • D latum is found in temperate regions

Clinical Findings

Symptoms and Signs

  • Large tapeworm infections are generally asymptomatic

  • Nonspecific gastrointestinal symptoms (eg, diarrhea)

  • Megaloblastic anemia and neuropathy can result from prolonged heavy infection

Differential Diagnosis

  • Beef, pork, dwarf, rodent, or dog tapeworm

  • Chronic fatigue syndrome

  • Chronic hepatitis

  • Irritable bowel syndrome

  • Amebiasis

  • Ascariasis

  • Enterobiasis (pinworm, mostly children)

  • Hookworm disease

  • Strongyloidiasis

  • Celiac disease or tropical sprue

  • Pernicious anemia (D latum)

Diagnosis

  • Diagnosis is usually made based on the identification of characteristic eggs or proglottids in stool

  • Egg release may be irregular, so examination of multiple specimens or concentration techniques may be needed

Treatment

Medications

  • Praziquantel

    • Treatment of choice

    • Single dose of 5–10 mg/kg is highly effective

    • Side effects include headache, malaise, dizziness, abdominal pain, nausea

  • Niclosamide

    • Alternative therapy

    • Single dose (2 g for adults chewed) is effective

    • Side effects include nausea, malaise, abdominal pain

Outcome

Follow-Up

  • A disintegrating worm is usually passed within 24–48 h of treatment. Since efforts are not generally made to recover and identify the scolex, cure can be presumed only if regenerated segments have not reappeared 3–5 months later

  • If it is preferred that parasitic cure be established immediately, the head (scolex) must be found in posttreatment stools; a laxative is given 2 h after treatment, and stools must be collected in a preservative for 24 h. To facilitate examination, toilet paper must be disposed of separately

When to Refer

  • If confirmation of the diagnosis is needed or if symptoms are progressive despite therapy

  • If there is difficulty distinguishing tapeworm-induced B12 deficiency from pernicious anemia

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