Liver Flukes

Key facts

• Liver flukes are parasitic flatworms that colonise the bile ducts and gallbladder, usually caught by eating raw or undercooked freshwater fish.
• Light infections often cause no symptoms; heavy or long-standing infections can lead to significant liver and bile duct damage.
• The main treatment is praziquantel, an antiparasitic that rapidly paralyses and kills the worms; a short course generally clears most fluke species.
• Anyone with prolonged unexplained fatigue or right-sided abdominal pain, especially after eating raw freshwater fish, should be investigated.

Symptoms and when to get checked

Many people carry a light burden of flukes for years without noticing anything. When symptoms do appear they typically include upper-right abdominal discomfort, fatigue, nausea, and intermittent fever. Chronic infection from species such as Clonorchis sinensis or Opisthorchis viverrini can cause recurrent bile duct blockages and, over decades, raises the risk of cholangiocarcinoma (bile duct cancer). Anyone with prolonged unexplained fatigue or right-sided abdominal pain, particularly after eating raw or undercooked freshwater fish, should be investigated.

Treatment

The mainstay of treatment is praziquantel, an antiparasitic that rapidly paralyses and kills the worms. A short course is generally effective against most fluke species. Follow-up stool testing a few weeks after treatment confirms the infection has cleared.

How it's caught

Liver flukes are picked up by eating raw or undercooked freshwater fish carrying the larval stage of the parasite. The larvae encyst in the fish's flesh and, once swallowed, migrate up the bile ducts, where the adult flukes can live and lay eggs for years if untreated. Cooking fish thoroughly before eating is the most effective way to prevent infection in the first place, since freezing or brief marinating does not reliably kill the larvae.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.