MSD Manual

Please confirm that you are a health care professional

honeypot link



Chelsea Marie

, PhD, University of Virginia;

William A. Petri, Jr

, MD, PhD, University of Virginia School of Medicine

Last review/revision Aug 2021 | Modified Sep 2022
View Patient Education
Topic Resources

Opisthorchiasis is infection with Opisthorchis viverrini (Southeast Asian liver fluke) or O. felineus (cat liver fluke), which are acquired by eating infected raw or undercooked fish that contains infectious metacercariae (encysted stage).

Flukes are parasitic flatworms that infect various parts of the body (eg, blood vessels, gastrointestinal tract, lungs, liver) depending on the species.

Opisthorchiasis due to O. viverrini occurs mainly in northeast Thailand, Laos, and Cambodia; O. felineus occurs mainly in Europe and Asia, including the former Soviet Union.

The life cycle of Opisthorchis requires both snails and fish. Dogs, cats, and other fish-eating mammals are also definitive hosts. After ingestion, metacercariae excyst and ascend through the ampulla of Vater into the biliary ducts, where they attach to the mucosa and mature. Adult flukes grow to 5 to 10 mm by 1 to 2 mm (O. viverrini) or 7 to 12 mm by 2 to 3 mm (O. felineus).

Opisthorchiasis resembles clonorchiasis Clonorchiasis Clonorchiasis is infection with the liver fluke Clonorchis sinensis. Infection is usually acquired by eating undercooked freshwater fish. Most infections are asymptomatic, but when present... read more Clonorchiasis and the development of symptoms depends on worm burden and duration of infection. Most O. viverrini infections remain asymptomatic, with about 5 to10% of patients presenting with symptoms that include right upper quadrant abdominal pain, indigestion, diarrhea, flatulence, and fatigue. Acute symptoms are more common with O. felineus infection and can include high-grade fever, anorexia, nausea, vomiting, abdominal pain, malaise, myalgia, arthralgia, and urticaria. Symptoms typically begin 10 to 26 days after exposure.

Diagnosis of opisthorchiasis is by finding eggs in the feces. Ultrasonography, CT, MRI, cholangiography, or endoscopic retrograde cholangiopancreatography (ERCP) may show biliary tract abnormalities.

The treatment of choice for opisthorchiasis is one of the following:

  • Praziquantel 25 mg/kg orally 3 times a day for 2 days

  • Albendazole 10 mg/kg orally once a day for 7 days

Infection can be prevented by cooking freshwater fish.

General references

  • 1. Xia J, Jiang SC, Peng HJ: Association between liver fluke infection and hepatobiliary pathological changes: A systematic review and meta-analysis. PLoS One 10 (7):e0132673, 2015. doi: 10.1371/journal.pone.0132673. eCollection 2015.

  • 2. Psevdos G, Ford FM, Hong S-T: Screening US Vietnam veterans for liver fluke exposure 5 decades after the end of the war. Infectious Diseases in Clinical Practice 26(4):208–210, 2018. doi: 10.1097/IPC.0000000000000611.

View Patient Education
NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
quiz link

Test your knowledge

Take a Quiz!