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Fluke Infections of the Liver

By Richard D. Pearson, MD, University of Virginia School of Medicine

Certain species of flukes cause infections of the liver.

  • People are infected when they swallow cysts containing fluke larvae in raw, undercooked, dried, salted, or pickled freshwater fish or on contaminated watercress.

  • Severe infection may cause a fever, chills, abdominal pain, jaundice, itching, diarrhea, vague discomfort, and weight loss.

  • Doctors diagnose the infection when they see eggs in a person's stool or in the contents of the intestine.

  • Depending on the type of fluke, drugs such as praziquantel, albendazole, or triclabendazole can eliminate them.

Liver fluke infections occur in Europe, Africa, the Far East, and South America but are rare in the United States. Flukes that cause infections of the liver include

  • Clonorchis sinensis, which causes clonorchiasis

  • Fasciola hepatica, which causes fascioliasis and typically infects sheep and cattle

The life cycle of flukes is complex. People get liver fluke infections when they swallow cysts containing immature flukes (larvae) in raw, undercooked, dried, salted, or pickled freshwater fish or in watercress contaminated by sheep or cattle dung.

After the cysts are swallowed, the larvae leave the cysts in the intestines and travel back up the intestine and enter the bile duct (the tube that carries bile from the liver and gallbladder to the intestine). Then they go up the bile duct into the liver and sometimes the gallbladder. There, they develop into adults and produce eggs. Eggs are passed in the stool and ingested by snails. Infected snails release immature flukes that can swim (called cercariae). Cercariae released from infected snails form cysts in various freshwater fish or attach to certain aquatic plants, depending on the type of fluke.

Symptoms

Usually, these fluke infections cause no symptoms. But if the infection is severe, people may have a fever, chills, and abdominal pain. If flukes block enough of the bile passages inside or outside the liver, people may develop yellowing of the skin and whites of the eyes ( jaundice), itching, diarrhea, and weight loss. Sometimes the flukes damage the liver, causing fibrosis or cirrhosis.

Years later, infected people may develop gallstones, pancreatitis, or cancer of the biliary ducts.

Diagnosis

  • Examination of a stool sample

Doctors diagnose liver fluke infections when they see eggs in a person's stool (feces) or in the contents of the person's intestines.

Treatment

  • A drug that eliminates flukes from the body (an antihelminthic drug)

  • Sometimes surgery

Liver fluke infections are treated with a drug that eliminates flukes from the body, such as praziquantel or albendazole (for clonorchiasis) or triclabendazole, bithionol, or nitazoxanide (for fascioliasis).

If the flukes block the bile ducts, surgery may be necessary.

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* This is the Consumer Version. *