A combination of liver fluke infection and traditional northeastern Thai foods associated with cholangiocarcinoma development

Opisthorchis viverrini infection is one of the risk factors for cholangiocarcinoma (CCA) in northeast Thailand, a region with one of the highest reported incidence rates of CCA. The traditional practice of eating raw fish, repeated exposure to liver flukes, and consumption of nitrosamine-contaminated food are major risk factors for CCA. So far, there have been no reports about which northeastern traditional dishes may be involved in CCA development. The present study, thus, investigated the effects of traditional foods. It focused specifically on the consumption of fermented foods in combination with O. viverrini infection in hamsters. Syrian hamsters were divided into six groups: (i) normal hamsters, (ii) O. viverrini infection only and (iii)–(vi) O. viverrini infection plus fermented foods (pla som—fish fermented for 1 day), som wua—fermented beef, som phag—fermented vegetables, and pla ra—fish fermented for 6 months. Syrian hamster livers were used for analysis of histopathological changes through hematoxylin and eosin; Sirius Red; and immunohistostaining for cytokeratin-19, proliferating cell nuclear antigen, and CA19-9. Hamster sera were used for liver and kidney function tests. Results of all O. viverrini-infected groups and fermented food groups showed that histopathological changes consisted primarily of aggregations of inflammatory cells surrounding the hepatic bile duct, especially at the hilar region. However, there was a difference in virulence. Interestingly, aggregations of inflammatory cells, new bile duct formation, and fibrosis were observed in subcapsular hepatic tissue, which correlated to positive immunohistochemical staining and increased liver function test. The present study suggests that fermented food consumption can exacerbate cholangitis and cholangiofibrosis, which are risk factors for cholangiocarcinoma-associated opisthorchiasis.