Temperature and Preparation Time Intervals on Survival of Opisthorchis viverrini Metacercariae in Pickled Fish (Pla-som).

This study involved two series of independent trials that investigated the storage temperature and time of raw fish to eliminate Opisthorchis viverrini metacercarial infection in Thai pickled fish. A total of 330 healthy silver barb fishes (30-day posthatch) were infected with O. viverrini cercariae at an inoculation ratio of 50 cercariae/fish. After infection, the fish was reared for 3 months. The first trial was to evaluate the effect of fish storage temperature in the recovery from O. viverrini metacercariae. The infected fishes were randomly divided into five groups and stored at -20°C, 2°C, 4°C, and 8°C or room temperature (as a control) for 24 h. The results showed that at a storage temperature of -20°C, the fish initially had a reduced recovery rate from O. viverrini metacercariae. The second trial investigated the storage time for the recovery of infected fish stored at -20°C for 18, 24, 36, 48, or 60 h and used room temperature as a control group. The results revealed that storing infected fish at -20°C for 48 and 60 h had the lowest recovery rate from O. viverrini metacercariae at 0.00%. In conclusion, storing infected fish at a temperature of -20°C for a period of 48 h or longer could restrict the O. viverrini metacercaria recovery rate. These results were recommended as suitable conditions for the preparation of Pla-som to avoid O. viverrini metacercaria contamination.