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For further information, see CMDT Part 35-14: Fascioliasis

Key Features

  • Infection results from ingestion of encysted metacercariae on watercress or other aquatic vegetables or in water

  • Eggs of worm infect snails; snails subsequently infect vegetation

  • Most prevalent in sheep-raising countries, particularly where raw salads are eaten

Clinical Findings

  • Symptoms related to migration of larvae present 6–12 weeks after ingestion

  • Typical findings

    • Abdominal pain

    • Fever

    • Malaise

    • Weight loss

    • Urticaria

    • Eosinophilia

    • Leukocytosis

  • Tender hepatomegaly and elevated liver function tests may be seen

  • Migration to other organs may lead to localized disease (rare)

  • Symptoms of worm migration subside after 2–4 months, followed by

    • Asymptomatic infection by adult worms

    • Intermittent symptoms of biliary obstruction, with biliary colic and, at times, findings of cholangitis


  • Eggs are not found in the feces during the acute migratory phase of infection

  • Clinical suspicion should be based on clinical findings and marked eosinophilia in at-risk individuals

  • Imaging studies

    • Show hypodense migratory lesions of the liver

    • In chronic infection, show masses obstructing extrahepatic biliary tract

  • Serologic assays have sensitivity and specificity > 90%, but cannot distinguish past and current infection

  • Antigen tests with excellent sensitivity and specificity are available in veterinary medicine and show promise in humans

  • Definitive diagnosis is made by identifying eggs in stool

  • Repeated examinations may be necessary


  • Praziquantel not effective

  • Triclabendazole

    • Treatment of choice

    • Available in the United States through the CDC under an investigational protocol

    • Standard dosing of 10 mg/kg orally in a single dose or two doses over 12 hours achieves a cure rate of about 80%

    • Repeat dosing is indicated if abnormal radiologic findings or eosinophilia do not resolve

  • Bithionol

    • Second-line drug

    • 30–50 mg/kg/day in three divided doses on alternate days for 10–15 days

    • Not available in the United States

  • Treatment with either drug can be accompanied by abdominal pain and other gastrointestinal symptoms

  • Other potential therapies

    • Emetine and dehydroemetine, both widely used in the past but quite toxic

    • Nitazoxanide

  • Prevention of fascioliasis involves avoiding ingestion of raw aquatic plants

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