Fascioliasis

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

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

• Not available in the United States

• 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