Doctor Warns Raw Fish Parasites Can Cause Liver Cancer
A hospital doctor warns that liver fluke parasites found in raw or undercooked freshwater fish can cause bile duct cancer, with symptoms often appearing years after infection.
On July 8, 2025, Dr. Jetsada Bunyanvongvirooj, deputy director of Maha Sarakham Hospital, posted a detailed health warning on his Facebook page "Doctor Jetsada" explaining the dangers of liver fluke parasites commonly found in raw or undercooked freshwater fish dishes popular in Thailand.
The liver fluke (Opisthorchis viverrini) is a tiny flatworm that lodges in the bile ducts and causes chronic inflammation, eventually leading to bile duct cancer. The parasite is microscopic and invisible to the naked eye. Even eating raw fish dishes like fermented fish (pla raa) or briefly cooked dishes carries risk, as does simply tasting contaminated food.
Dangerous eating habits include consuming raw fish in som tam (papaya salad), eating fermented or salted fish with partially raw flesh, cooking fish at insufficient temperatures (below 70°C), using the same utensils for raw and cooked food, and tasting food before it has been properly heated. The parasite can survive salting, pickling, and brief cooking.
Symptoms often appear years after infection and may include vague discomfort below the right rib cage, bloating, loss of appetite, weight loss, chronic fatigue, low-grade fever, and yellowing of skin and eyes. Prolonged infection (10-20 years) can cause severe scarring or cancer without warning signs.
Detection methods include stool examination for parasite eggs, ELISA blood tests to detect antibodies, and ultrasound imaging to identify abnormalities in the bile ducts. The doctor advises people in high-risk areas or those with a history of eating raw fish to get tested, while emphasizing that proper cooking (heating to 70°C for at least 5 minutes) safely eliminates the parasite.
