Undercooked 'pla ra' targeted after thousands test positive for liver fluke

PUBLISHED : 7 Jul 2026 at 13:31

Thousands of university freshmen have tested positive for liver fluke infection in Maha Sarakham, prompting wide-ranging inspections targeting the use of undercooked fermented fish at somtam shops in the northeastern province.

The initial results were obtained using urinary antigen test kits (UATs), a faster testing method developed in recent years, Public Health Minister Pattana Promphat said on Tuesday. Stool examinations were still required to confirm the presence of the infection (opisthorchiasis),

At Mahasarakham University, 4,233 of the 12,733 first-year students tested positive, about 33%. At Rajabhat Maha Sarakham University, 380 of 1,922 students tested positive, about 19%.

Local healh officials described the test results as "alarming". The average infection rate among the general population in the province was about 11%.

They stressed the urgent need to promote safer eating habits.

Health inspections have been ordered for all somtam shops near the two universities, and also restaurants that use pla ra, or Isan fermented fish, in their dishes, Maha Sarakham governor Chumpit Decharat said.

Restaurants that meet safety standards will receive a sign they can display for customers  affirming that, “This restaurant serves cooked and safe pla ra.”

Dr Jade Boonyawongvirot, deputy director of Maharat Nakhon Ratchasima Hospital, warned of the likely long-term consequence if people's eating habits do change. It may not become apparent immediately but could emerge in 15 or 20 years time in the form of bile duct cancer (cholangiocarcinoma), a disease that was difficult to treat and with a high mortality rate.

He said the liver fluke is a parasite commonly found in Thailand, particularly in the Northeast and Northern regions, and in neighbouring countries such as Laos and Cambodia.

The scientifically confirmed source of infection was raw or undercooked freshwater fish. While these fish were used to make pla ra, he said, that did not mean pla ra was solely to blame for the high infection rate.

“If pla ra is produced to proper hygienic standards, fermented correctly and boiled before consumption, the risk is very low,” Dr Jade said.