Merck Manual

Please confirm that you are a health care professional

honeypot link

Opisthorchiasis

By

Richard D. Pearson

, MD, University of Virginia School of Medicine

Last full review/revision Jan 2020| Content last modified Jan 2020
Click here for 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.

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. Human disease resembles clonorchiasis and is acquired by eating raw or undercooked freshwater fish that contains infectious metacercariae (encysted stage). 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).

Most infections are subclinical. Symptoms of opisthorchiasis include vague gastrointestinal discomfort, diarrhea, and constipation. In chronic infection, symptoms may be more severe; hepatomegaly and undernutrition may be present. Rare complications include cholecystitis, cholangitis, and cholangiocarcinoma (bile duct cancer [1]). Vietnam veterans who develop cholangiocarcinoma may have been infected with O. viverrini or Clonorchis sinensis while they served in Southeast Asia (2).

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.

Click here for Patient Education
NOTE: This is the Professional Version. CONSUMERS: Click here for the Consumer Version

Test your knowledge

Human Papillomavirus (HPV) Virus
Human papillomavirus (HPV) infection is the most common sexually transmitted infection and can cause skin warts, genital warts, or certain cancers. Of the many different strains of HPV, which of the following is most likely to cause visible genital warts?
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID

Also of Interest

Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
Download the Manuals App iOS ANDROID
TOP