Infectious Agent

Trematode flatworms Fasciola hepatica and F. gigantica .


Consumption of watercress or other aquatic plants contaminated with infective metacercariae or contaminated freshwater.


Broadly distributed. The highest rates of F. hepatica infection have been reported from Bolivia, Peru, Egypt, Iran, Portugal, and France. F. gigantica has a more limited distribution (parts of Africa, the Middle East, and South and East Asia).

Clinical Presentation

The acute phase begins 6–12 weeks after exposure and can last up to 4 months. Most infected people are asymptomatic, but findings might include marked eosinophilia, abdominal pain, intermittent high fever, weight loss, or urticaria. Within weeks to months, symptoms of the acute phase subside as worms enter the bile ducts, beginning the chronic phase. Chronically infected people in this phase may also be asymptomatic or may present with biliary colic, epigastric pain, nausea, jaundice, or pruritus. The long-term prognosis depends on the extent of the liver and biliary damage.


Detection of eggs in stool or duodenal or biliary aspirates. Serologic tests may be useful during the acute phase, since egg production does not start until 3–4 months after exposure. Serologic testing is available through CDC (www.cdc.gov/dpdx; 404-718-4745; parasites@cdc.gov). Radiologic examinations, including ultrasonogram and CT of the liver, can be helpful, especially during the hepatic or migratory acute phase.


First-line treatment is with triclabendazole, which is not commercially available for human use in the United States; it is available to US-licensed physicians through the CDC Drug Service, under a special protocol, which requires both CDC and FDA to agree that the drug is indicated for treatment of a particular patient (404-718-4745; parasites@cdc.gov). An alternative drug is nitazoxanide. Surgical resection or endoscopic retrograde cholangiopancreatographic removal of adult flukes can be done in cases with biliary tract obstruction.


Avoid eating uncooked aquatic plants, including watercress, especially from endemic grazing areas; avoid drinking untreated freshwater.

CDC website: www.cdc.gov/parasites/fasciola


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LeAnne M. Fox