Fermented and pickled fish full of parasites

The Parasitic Disease Research Center of Suranaree University of Technology (PDRC) has tested fermented fish from 73 markets in the provinces of the northeastern region (Isan) Thailand. PDRC revealed the results on their Facebook Page on 24 May 2020. There are many types of fermented fish and pickled fish in Thailand that can be found in all provinces across the country. One of the most famous dishes with fermented fish is Papaya Salad called Som Tam Plara in Thai. Many might prefer eating the fish raw, this research will help remind us to eat such dishes cooked for our own safety.


9.58% of the fermented and pickled fish samples from Sisaket, Khon Kaen, Mukdahan, Sakon Nakhon, and Udon Thani are found with liver fluke and intestinal flukes, these are a polyphyletic group of parasites. Most of these parasites are found in fermented fish. Samples of pickled fish were collected from 20 provinces in the northeastern region of Thailand, metacercaria was found in 20.2% of these samples. The definition of metacercaria according to Merriam-Webster is a tailless encysted late larva of a digenetic trematode that is usually the form that is infective for the definitive host.


Samples of fermented and pickled fish were collected from 5 Districts in Udonthani and 7 Districts in Kalasin. 9.1% of fermented fish and 42.9% of pickled fish were found with parasites. These contaminated samples came from Kumpawapee and Kudjub in Udonthani Province. The samples of pickled fish showed parasites on days 1-4 when stored at room temperature. Hamsters were given the samples with liver fluke, 52% were infected with the parasite when given samples of day 1, 44.7% were infected with the parasite when given samples of day 2, the infection rate for day 3 and 4 were 11.3% and 1%.


Credit: Khaosod


The samples of pickled fish stored at a temperature of 4C for 3 days showed that 3.3% of hamsters were infected when given samples of day 1, and 12,7% were infected when given samples of day 2. Hamsters were not infected when given samples of day3-5.


There are easy ways to kill these parasites found in Carp fishes.

  1. Microwave the food at 400W or 800W for 5 minutes, or boil the food at 90C for 5 minutes.
  2. Freeze the food at -20C for 48 hours.

Pickled fish stored at 4C for 24-48 hours showed an infection rate of 40% when given to hamsters.


FB Caption: 42.9% of the pickled fish samples were found with parasites.


Source: Khaosod, PDRC