Main content area

Nocardia seriolae infection in the cultured eel Anguilla japonica in Korea

Kim, Jin Do, Lee, Nam‐Sil, Do, Jeung Wan, Kim, Myoung Sug, Seo, Han Gill, Cho, Miyoung, Jung, Sung Hee, Han, Hyun‐Ja
Journal of fish diseases 2018 v.41 no.11 pp. 1745-1750
Anguilla japonica, Nocardia seriolae, bacteria, eel, farmed fish, fish farms, granuloma, hemorrhage, mortality, pathogenicity, phylogeny, recirculating aquaculture systems, ribosomal DNA, ribosomal RNA, spring, summer, Korean Peninsula
Mass mortality occurred at an Anguilla japonica eel farm equipped with a recirculating aquaculture system in Gimcheon, Korea, from late spring to early summer 2015. The cumulative 3‐month mortality was 16% (approximately 24,300–150,000 fish). The majority of affected fish displayed ulcerative lesions that progressed to petechial haemorrhages and small white granulomas in the major organs. A Gram‐positive, acid‐fast, nonmotile bacterium was isolated from internal organ lesions. Phylogenetic analysis of 16S rRNA identified the species as Nocardia seriolae and the strain was designated EM150506. Afterwards, naïve eels were injected with 1.8 × 10⁷ colony‐forming units per fish to confirm the strain's pathogenicity, which resulted in a 20% mortality rate within 4 weeks. However, surviving fish still exhibited white N. seriolae colonies in internal organs. To our knowledge, this is the first report of a N. seriolae infection in cultured eel.