Liver Flukes: How Raw Food Leads to Bile Duct Cancer

     In Thai culinary culture, especially in the Northeast and North regions, raw freshwater fish dishes are considered a long-standing delicacy. However, beneath that deliciousness lies a serious, silent threat known as "Liver Flukes." This infection acts as a starting point leading to chronic inflammation in the bile duct system and can develop into Cholangiocarcinoma (Bile Duct Cancer), which causes a significant number of deaths among Thai people each year.

Liver Fluke Disease

     Liver Fluke Disease (Liver Flukes) in Thailand is mostly caused by the parasite species Opisthorchis viverrini. This parasite is flat and leaf-like in shape, with narrow and rounded ends, measuring about 5-10 mm. The adult flukes live in thebile ducts inside the human liver, as well as in reservoir hosts like dogs and cats. Once the parasites mate, they lay a vast number of eggs, which mix with the bile into the intestines and are excreted with feces.

If defecation occurs outside of a proper toilet and the eggs drop into water sources, their life cycle begins anew through freshwater snails and fish.

Symptoms of Liver Fluke Infection

The terrifying aspect of this disease is that in the early stages, it is usually asymptomatic, leaving patients unaware of their infection. However, as the parasite load increases or if left untreated for a long time, the prominent symptoms will begin to appear as follows:

1. Initial Symptoms

• Bloating, flatulence, and abdominal discomfort from time to time.
• Some individuals may feel a tightness or fullness under the right rib cage or epigastrium.

2. Severe Symptoms

     When the parasites cause chronic irritation and inflammation, patients will experience loss of appetite, weight loss, fatigue, low-grade fever, and begin to show signs of jaundice, namely yellow skin and yellow eyes due to the obstruction of the bile ducts.

3. Advanced Stage

     If it progresses to bile duct cancer, symptoms such as hepatomegaly (enlarged liver), ascites (fluid retention in the abdomen), and permanent liver damage will occur, ultimately leading to death.

Causes

The primary cause is the dietary habit of eating raw or undercooked scaled freshwater fish from the Cyprinidae family, such as Siamese mud carp, Barb fish, and Hampala barb. High-risk dishes include:

• Koi Pla (raw fish salad), raw fish Larb
• Pla Som (fermented fish), Pla Jom, Mum Pla
• Pla Ra / Fermented fish paste (that has not been boiled/cooked)

In addition, sanitation factors, such as defecating into water sources or outside of proper restrooms, are major causes of spreading parasite eggs into the environment.

Prevalence of the Disease

The liver fluke situation in Thailand remains severe, with noteworthy statistics as follows:

• Number of Infections: It is estimated that no fewer than 6 million Thai people are infected.
• High Prevalence Areas: Most commonly found in the Northeast (Isan) and Northern regions. Particularly in Isan, the incidence rate of bile duct cancer is found to bethe highest in the world.
• Demographics: It is found in males about 2.5 times more than females, due to a higher frequency of high-risk eating habits.
• Mortality Rate: There are approximately 15,000 - 20,000 deaths from bile duct cancer per year (which can progress from liver fluke disease to bile duct cancer over the next 20-30 years).

Diagnosis of Liver Fluke Disease

• Stool Examination: The easiest and gold standard method. Stool samples are examined under a microscope to look for parasite eggs, which characteristically resemble small light bulbs with a golden-brown hue.
• Urine Test: A novel diagnostic technology that detects liver fluke antigens or secretions in the urine of infected individuals.
• Other Methods: In some cases, immunological tests may be used in conjunction.

Screening for Complications and Bile Duct Cancer

• Ultrasound: A method used by physicians to visualize the liver and bile ducts. This technique can detect abnormalities such as bile duct wall thickening or early cancerous masses.
• Radiology: Other radiological imaging methods may be utilized based on the physician's discretion for a more precise diagnosis.

Guidelines for Prevention and Treatment

Current treatment involves the medication Praziquantel, which yields excellent results. However, taking medication alone cannot provide a sustainable solution if raw fish consumption habits persist. The best prevention follows the 5 principles (in Thai called "5 S", translated here for medical practices):

• Cooked (Suk): Only consume fish thoroughly cooked with heat.
• Clean (Sa-ard): Wash hands thoroughly before preparing and consuming food.
• Sanitation (Sukhathan): Defecate only in sanitary, proper restrooms.
• Submit (Song Truat): If there is a history of raw fish consumption, submit stool samples for parasite egg screening at least once a year.
• Public Health (Satharanasukh): Receive immediate treatment if an infection is found, and permanently cease raw fish consumption.

References

• Department of Disease Control, Ministry of Public Health. (2021). The New Generation Unites to Eliminate Liver Flukes and Cholangiocarcinoma. Retrieved July 9, 2026, from https://ddc.moph.go.th/uploads/publish /1149120210529085028.pdf [Online]
• Kosol Rungreungchai. (2010). Liver Flukes... A Risk Factor for Cholangiocarcinoma. Retrieved July 9, 2026, from https://www.si.mahidol.ac.th/th/healthdetail.asp?aid=779 [Online]
• Hospital for Tropical Diseases. (2020). Liver Fluke Disease. Retrieved July 9, 2026, from https://www.tropmedhospital.com/knowledge/846131.html [Online]
• Centers for Disease Control and Prevention. (2024). About Liver Flukes. Retrieved July 9, 2026, from https://www.cdc.gov/liver-flukes/about/index.html [Online]