PATTAYA, Thailand – Doctors have warned that liver fluke infections are caused by consuming freshwater fish containing parasite larvae that have not been properly cooked, while clarifying that not all fermented fish products are dangerous. The warning follows recent health screenings among newly enrolled university students in Maha Sarakham province, where thousands were found to have liver fluke infections. Dr. Jessada Boonyawongwirot, Deputy Director of Maharat Nakhon Ratchasima Hospital, said the clearest scientific evidence shows that liver fluke infection occurs through eating raw or undercooked freshwater fish containing parasite larvae.
He explained that high-risk dishes include koi pla (raw fish salad), larb pla (spicy minced fish salad), traditional raw fish dishes, pla som that has not been fermented long enough, and pla chao or other fermented fish products that have not been heat-treated. However, he stressed that fermented fish products such as pla ra should not be blamed in all cases. Properly produced fermented fish that follows food safety standards and is thoroughly cooked before consumption carries a much lower risk. Dr. Jessada made the comments after reports that liver fluke screening among first-year students at universities in Maha Sarakham found high infection rates.
Mahasarakham University detected infections in 4,233 out of 12,733 students, or around 33 percent, while Rajabhat Maha Sarakham University found 380 infections among 1,922 students, or about 19 percent. Screening of more than 20,000 residents across the province also found an average infection rate of around 11 percent. He said liver fluke disease is often a “silent” illness, as infected people may show no symptoms for many years. Long-term infection is strongly linked to an increased risk of bile duct cancer, a serious disease that is difficult to treat and has a high mortality rate.
“Recent reports show that liver fluke infection is not only a problem among older generations but also among young people. If eating habits are not changed today, the consequences may appear 15 to 20 years later in the form of bile duct cancer,” Dr. Jessada said. The liver fluke Opisthorchis viverrini is commonly found in Thailand, especially in the northeastern and northern regions, as well as neighboring countries including Laos and Cambodia. Health officials said the best prevention is to avoid eating raw or undercooked freshwater fish and ensure that fermented fish products are properly prepared and cooked before consumption.
Doctors also reassured fans of popular Thai dishes such as som tam with pla ra, including many foreign visitors who enjoy the dish that the risk does not come from papaya salad itself. They cautioned against generalizing that all fermented fish dishes are unsafe, noting that properly produced pla ra prepared according to food safety standards and cooked thoroughly carries a much lower risk of transmission. (TNA)
