Researchers have found that an increase in incidence of liver cancer in north-east Thailand is linked to a raw fish delicacy called koi pla, according to a BBC report. Koi pla is made from small fish caught from rivers and lakes in the region.

Opisthorchis viverrini are the major risk factors for the development of HCC and CCA, respectively./CDC
Opisthorchis viverrini are the major risk factors for the development of HCC and CCA, respectively./CDC

So what’s the connection between this traditional dish and liver cancer? The liver fluke.

Dr. Banchob Sripa at the Tropical Disease Research Laboratory in Khon Kaen University has been studying this issue for decades and provided some interesting numbers:

The BBC reports:

His team found that in some communities up to 80% of people were infected by the fluke, some as young as four years-old, but that the cancer rarely developed before people reached 50. Once it does, though, there is little hope for patients.

At the university hospital they receive around 2,000 patients a year with a specific form of liver cancer called cholangiocarcinoma.

Only around 200 of those can be treated, usually by surgery, cutting out the tumour from the liver.

The others are given palliative care, easing their discomfort, usually by draining bile ducts, until they die.

In Thailand, infection with liver flukes often involve consuming koi pla, a raw fish dish or other ingestion of undercooked, salted, pickled, or smoked freshwater fish mostly of the cyprinid variety.

According to the CDC, most infections of Opisthorchis and Clonorchis are asymptomatic. In mild cases, manifestations include dyspepsia, abdominal pain, diarrhea or constipation. With infections of longer duration, the symptoms can be more severe, and hepatomegaly and malnutrition may be present.

Opisthorchis viverrini is the major risk factors for the development of hepatocellular carcinoma (HCC). Untreated cases can also lead to cholangitis, cholecystitis, and chlolangiocarcinoma.

The eggs of the two parasite seen microscopically are essentially indistinguishable, however a 2009 study in Central Thailand showed that using PCR techniques on positive Opisthorchis-like egg positive samples to be 64% and 23% of individuals to be infected with O. viverrini and C. sinensis, respectively.

The best preventive measures against these liver parasites is not eating raw seafood, especially fish.

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