• Journal of fish pathology
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• v.36 no.2
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• pp.239-250
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• 2023

Disease monitoring was conducted to investigate the recent disease occurrence in Japanese eels (Anguilla japonica). Between May 2021 and March 2022, an investigation was conducted on eels from seven farms experiencing mortality. JEECV (Japanese eel endothelial cells-infecting virus) was detected in all examined farms, each exhibiting co-infections with 1 or 2 bacteria, including Edwardsiella anguillarum, E. piscisida, Aeromonas sp., Citrobacter freundii, Lactococcus garviae, or Vibrio sp. From March 2022 to October 2023, monthly periodic inspections were carried out at a farm in Yeonggwang, Jeollanam-do, for a total of 22 times. JEECV was detected in 10 out of 22 times, even when mortality was not recorded. Bacteria such as E. anguillarum, C. freundii, Aeromonas sp., and Vibrio sp. were isolated, but consistent clinical signs of liver abscess and hemorrhagic lesions were only recognized in fish infected with E. anguillarum. Other bacteria were often isolated from apparently healthy fish. In conclusion, mortality in eel farms frequently occurs due to co-infections of JEECV with bacteria rather than JEECV alone. Therefore, to reduce eel mortality, it is crucial to decrease co-infections, with a particular emphasis of JEECV and E. anguillarum.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.54 no.5
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• pp.668-675
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• 2021

The infection status of domestic farmed eels Anguilla japonica, Anguilla bicolor and Anguilla marmorata with Japanese eel endothelial cell-infecting virus (JEECV) and anguillid herpesvirus 1 (AnHV) was examined at the major eel farming areas in Korea. These viruses were detected in all areas examined, regardless of the eel species or age. Any farm with a history of viral infection in adult fish confirmed the infection to be transmitted to stocked fry within 3 to 5 months. It is proposed that both viruses are horizontally transmitted within a given farm. The primary symptoms and histopathological lesions produced by the two viral infections are similar, making it difficult to distinguish the two diseases through clinical symptoms. Both viruses displayed 100% detection in the gills, suggesting that the gills are an optimal tissue for JEECV and AnHV monitoring. This study concluded that JEECV and AnHV were prevalent on eel farms across the country and caused very high mortality when the two viruses co-infected fry. Additional studies, including experimental infections, are needed to clearly understand the pathogenicity of each virus and the risk of co-infection.

• Korean Journal of Ichthyology
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• v.30 no.4
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• pp.185-193
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• 2018

From 2017 to 2018, the disease has been monitored at four culturing eel farms in Incheon and Gyeonggi region in Korea. As a result, diseases with gill congestion frequently occurred. This disease occurred regardless of size of eel, but the frequency and cumulative mortality were high in eels within 3 months after stocking. The infected fish showed pathological histopathological features such as intense congestion and dilation in the central venous sinus (CVS) of gill filaments and hemorrhages in liver and kidney. Hexagonal viral particles measuring about 70 nm in diameter was observed in nuclei and cytoplasm of gill vascular endothelial cells. Molecular biologic diagnosis by both PCR and genetic analysis has been revealed that the causative agent of this disease is Japanese eel endothelial cells-infecting virus (JEECV), the cause of viral endothelial cell necrosis of eel (VECNE), which is mainly reported in Japan. This study is the first report on the characteristics of JEECV and VECNE infection in domestic eel farms.