Carcinogenic Liver Fluke and Others Contaminated in Pickled Fish of Northeastern Thailand

Twenty provinces in northeastern Thailand were investigated for fluke metacercariae contamination in pickled fish, or pla-som, during January –June 2016. A total of 129 pickled fish shops were randomly chosen. Samples were digested with acid-pepsin and those found to be infected with metacercariae were fed to hamsters to test for metacercariae infectivity. The results demonstrated that only 20.2% of the pla-som samples were infected with fluke metacercariae (mc), at various levels (1 to 268 mc/kg). All recovered fluke metacercariae were inactive, degenerated and could not develop to adults in the animal model. In conclusion, the fluke mc infection status in pla-som was correlated with the prevalence of fluke infection in this region known for high O.viverrini and cholangiocarcinoma development. Clearly, systematic control of the fluke life cycle is needed. Whether pickling is an effective preventive measure needs further assessment.