Flukes are parasitic flatworms that infect various parts of the body (eg, blood vessels, gastrointestinal tract, lungs, liver) depending on the species.
F. hepatica is the sheep and cattle liver fluke. Incidental human fascioliasis, acquired by eating watercress contaminated by sheep or cattle dung, occurs in Europe, Africa, China, and South America but is rare in the US.
In acute infection, immature flukes migrate through the intestinal wall, the peritoneal cavity, the liver capsule, and the parenchyma of the liver before entering the biliary ducts where they mature to adulthood in about 3 to 4 months. The adults lay eggs, which are passed through the bile ducts into the duodenum and then out in the stool.
Symptoms and Signs of Fascioliasis
Acute infection can cause abdominal pain, hepatomegaly, nausea, vomiting, intermittent fever, urticaria, malaise, and weight loss due to liver damage.
Chronic infection may be asymptomatic or lead to intermittent abdominal pain, cholelithiasis Cholelithiasis Cholelithiasis is the presence of one or more calculi (gallstones) in the gallbladder. In developed countries, about 10% of adults and 20% of people > 65 years have gallstones. Gallstones... read more , cholangitis, obstructive jaundice Jaundice Jaundice is a yellowish discoloration of the skin and mucous membranes caused by hyperbilirubinemia. Jaundice becomes visible when the bilirubin level is about 2 to 3 mg/dL (34 to 51 micromol/L)... read more , or pancreatitis Overview of Pancreatitis Pancreatitis is classified as either acute or chronic. Acute pancreatitis is inflammation that resolves both clinically and histologically. Chronic pancreatitis is characterized by histologic... read more .
Heavy infection can cause sclerosing cholangitis Primary Sclerosing Cholangitis (PSC) Primary sclerosing cholangitis (PSC) is patchy inflammation, fibrosis, and strictures of the bile ducts that has no known cause. However, 80% of patients also have inflammatory bowel disease... read more and biliary cirrhosis. Ectopic lesions may occur in the intestinal wall, lungs, or other organs.
Pharyngeal fascioliasis that results in dysphagia has been reported after consumption of infected raw liver in the Middle East; this infection is called halzoun.
Diagnosis of Fascioliasis
Microscopic examination of stool or duodenal or biliary material for eggs
Fascioliasis should be considered in patients with abdominal pain and/or hepatomegaly, and a dietary history of watercress ingestion or consumption of raw vegetables exposed to contaminated water.
When fascioliasis is suspected, patients should have stool examination for eggs and serum antibody assay. Supportive findings on blood and imaging tests done for evaluation of abdominal complaints include anemia, eosinophilia, abnormal liver tests, elevated erythrocyte sedimentation rate, and hypergammaglobulinemia, and hypodense lesions in the liver on CT scan during the acute stage of fascioliasis.
If stool examination and antibody testing are negative or equivocal but fascioliasis is still suspected (ie, based on numerous supportive findings, particularly eosinophilia), then endoscopy with duodenal and biliary aspiration should be done. Eggs and sometimes adult worms may be detected in specimens obtained during endoscopy.
Antibody detection assays are particularly useful in
The early stages of infection before eggs are produced (egg production typically begins at least 3 to 4 months after exposure)
Chronic infection when egg production is sporadic or low
Loss of detectable antibodies occurs 6 to 12 months after cure.
In chronic infections, eggs may be recovered from the stool or from duodenal or biliary materials. The eggs are indistinguishable from those of Fasciolopsis buski.
In endemic areas, eggs can also be seen in stool after ingestion of infected animal livers, which are not infective for humans, resulting in a misdiagnosis of fascioliasis. Thus, patients should be asked to follow a liver-free diet for several days before their stool is examined.
Ultrasonography, CT, MRI, endoscopic retrograde cholangiopancreatography (ERCP), or cholangiography can detect biliary tract abnormalities in chronic disease.
Treatment of Fascioliasis
Triclabendazole or possibly nitazoxanide
Treatment of fascioliasis for patients ≥ 6 years is with 2 doses of 10 mg/kg triclabendazole given 12 hours apart, orally with food. Nitazoxanide 500 mg orally twice a day for 7 days may be effective, but the data are limited.
Treatment failures are common with praziquantel; it is not recommended.
In some patients, extraction of adult flukes from the biliary tract by ERCP may be useful.
Prevention involves not eating watercress or other freshwater plants in regions where F. hepatica is endemic. Family members of infected people should be evaluated for fascioliasis.