Coincidence? Or just a fluke?


There are very many good reasons for westerners to wish to live in Thailand. Warm weather, cold beer, warm women and cold beer. That will do for a start.

However, there are also some drawbacks. Aren’t there always! Such things as a very difficult language for foreigners, being a phonetic one, complete with a different grammar from English. Then there is the 90 day reporting. Real estate ownership is another very thorny topic. But let’s not get too far down that track. There is an olfactory problem as well. And even though hotels will ban their guests bringing durian into the hotel, there is something much worse. Much, much worse.

Anyone who has a Thai partner will have come across the sauce called Pla-Ra. If the name is not familiar to you, the nauseating smell will be. Something akin to a cross between smelly socks and a dead rodent. I and many other westerners I know refuse to let it in the house and it is confined to triple sealed jars in the Thai kitchen out the back. For Westerners who have not had the pleasure, imagine anchovies with a rotting problem. But more on Pla Ra in a moment.

Now Thailand prides (deludes?) itself that it is the “hub” of everything from airports, fashion design and floral arrangements, but whilst these are all open to debate, there is one area where Thailand is supreme – and this is in Khon Kaen in Isaan in particular. It is the hub of the Southeast Asian liver fluke, which is a trematode parasite from the family Opisthorchiidae.

This little charmer called Opisthorchis viverrini gets inside your body, swims through to the gall bladder region where it reproduces and sucks your blood. The constant irritation leads to abdominal pain, the blood loss to anemia and even a special cancer of the gall bladder called a cholangiocarcinoma. Not a very nice little sucker, is he, our Opisthorchis viverrini.

How this parasite gets into our bodies is of interest and even more convoluted than most, coming from the egg stage and then being eaten by aquatic snails. The eggs then produce a free swimming larval stage, called cercaria. The cercaria then locate cyprinoid fish, encyst in the fins, skin and musculature of the fish, and become metacercaria. Places where you are likely to find this second intermediate host of Opisthorchis viverrini include freshwater and stagnant or slow-moving waters (ponds, river, aquaculture, swamps and rice fields).

These fish are netted by Thai fishermen and they prepare fish-based meals with local herbs, spices, and condiments. The finished dish, called koi-pla made of raw fish, is a dietary staple of many northeastern Thai villagers and the common source of infection with Opisthorchis viverrini.

Dishes of raw fish are common in the Isaan cuisine of Thailand, and include koi-pla, raw fish in spicy salad larb-pla, and salted semi-fermented fish dishes called Pla-Ra (yes, it’s him again). Infection is acquired when people ingest raw or undercooked fish dishes containing the live parasite.

Cholangiocarcinoma (CC) is the second most common primary hepatic malignancy in the world. CC accounts for approximately 10 – 25 percent of all hepatobiliary malignancies. There are considerable geographic and demographic variations in the incidence of CC. There are several established risk factors for CC, including parasitic infections.

Liver fluke infections occur in some Asian countries (read Thailand, and Khon Kaen in particular) when people eat raw or poorly cooked fish that are infected with these tiny parasite worms. In humans, these flukes can cause bile duct cancer. The one most closely related to bile duct cancer risk is our old friend Opisthorchis viverrini.

Studies from Thailand have found that people with CC were between 5 and 27 times as likely to have antibodies indicating infection with the parasite Opisthorchis viverrini than anyone else.

To avoid infection, do not eat raw fish, and only eat cooked fish, or fish that has been stored in the deep freeze for some time to kill the Opisthorchis viverrini.

So now you have another reason to not allow Pla-Ra in the house, as well as the nauseating smell! By the way, we do have a GI and Liver Center if you’re worried!