Eel (Anguilla japonica) are the leading freshwater fish species with the highest nutritional value and added value, and are important fish species in the freshwater industry, accounting for 37% of freshwater fish production and 73% of production (KOSIS). Diseases occurring in domestic eels include bacterial pathogens such as Edwardsella sp. and Vibrio sp. and parasitic pathogens such as Pseudodactylogitus sp. and Trichodina sp. In particular, cases of damage caused by JEECV (Japanese eel endothelial cell infection virus) and AngHV1 (Jang et al., 2021; Kim et al., 2023), which are viral diseases that cause great damage to eels, have been reported recently. In the case of viral diseases, there are no effective drugs or vaccines, so fish farms are complaining of difficulties. In this study, we intend to contribute to the research and development of viral disease prevention in eels by monitoring pathogen infections in eel farms and constructing established fish cell line and primary cell line from eel’s fin. As a result of monitoring for pathogen infection, parasites were not detected, and bacterial diseases were mainly detected as Edwardsiella, and viral diseases were mainly detected as eel AngHV1. In addition, in farms where mass mortality was observed, the bacterial pathogen Edwardsiella sp. and the viral pathogen AngHV1 were most frequently detected as complex infections. Therefore, it is expected that virus and bacterial complex infections are likely to be involved in mass mortality, so care should be taken in disease management. In addition, no sensitivity was observed as a result of performing AngHV1 sensitivity tests using fish cell lines (BF-2, FHM, EPC, SSN-1) and established cell in eel"s fin. In the future, it is considered that further research on fish cell lines should be conducted to prevention of viral diseases.