Did You Know That This Thai Dish Can Cause Liver Fluke?

koi pla thailand dish
The finished dish of koi-pla accompanied by rice and vegetables. This dish is a dietary staple of many northeastern Thai villagers and is a common source of infection with Opisthorchis viverrini. (Image: Plos Medicine via Wikimedia CC BY 2.5)

Who doesn’t like Thai food? It’s so popular that in almost every town there is a Thai restaurant or two. But have you heard of koi pla? It is a popular meal in the northeastern region of Thailand. All you need to have is finely chopped raw fish, mixed with herbs, a dash of lime juice, and a sprinkling of live red ants, and serve it up raw. It is regularly eaten by the people of the Isaan region of the country. As nice as it may look, we all know looks can be deceiving.

Isan plateau in northeastern Thailand is a poor area and is home for around one-third of the country’s population. It is dry and not close to the sea, so they catch small fish from rivers and lakes to use in the dish. Most of the inhabitants are Lao in origin, and are renowned for their spicy and inventive cuisine, using whatever ingredients are available.

According to IFL Science, for a long time now, it’s been observed that people in the region have bizarrely high levels of the disease. It’s thought to account for more than half of all male cancer cases in the region, compared to a worldwide average of around just 10 percent. And it’s the little freshwater fish used in the dish that is the culprit, or more specifically, liver fuke or Opisthorchis viverrini, which is a food-borne trematode parasite from the family Opisthorchiidae that infects the bile duct. Doctors in the area are trying to educate people as to the risk koi pla poses, and it seems to be working.

An adult Opisthorchis viverrini showing (from top) oral sucker, pharynx, caecum, ventral sucker, vitellaria, uterus, ovary, Mehlis gland, testes, excretory bladder. (Image: Plos Medicine via Wikimedia CC BY 2.5)

An adult Opisthorchis viverrini showing (from top) oral sucker, pharynx, caecum, ventral sucker, vitellaria, uterus, ovary, Mehlis gland, testes, excretory bladder.
(Image: Plos Medicine via Wikimedia CC BY 2.5)

“We have been studying this link in our labs for over 30 years,” Dr. Banchob Sripa from the Tropical Disease Research Laboratory in Khon Kaen University told the BBC. “We found that the liver fluke can make a chemical that stimulates a host immune response—inflammation—and after many years, this becomes chronic inflammation, which then becomes cancer.”

But after over a decade of teaching the locals about the dangers of koi pla, the tide seems to be turning. Infection rates in some communities where over 80 percent, but now it seems to be dropping. It is led by the younger people, who now almost always cook the dish before eating it, though there are some older people who appear slightly more stubborn, wrote IFL Science.

“I think 60 percent do understand the causes of the liver cancer,” Dr. Banchob said to BBC News, “they are aware of the liver fluke. But 10 percent are still eating raw fish. I believe that 10 percent probably cannot change. So we should change the environment, make the fish cleaner, to get fewer infections.”

It is a good lesson for travelers. Make sure you watch what you eat and drink. There are still a lot of people who when overseas still take risks that are just not worth it.

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