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Susceptibility of freshwater rearing Asian seabass ( Lates calcarifer ) to pathogenic Streptococcus iniae
Author(s) -
Kayansamruaj Pattanapon,
Dong Ha Thanh,
Nguyen Vuong Viet,
Le Hai Dinh,
Pirarat Nopadon,
Rodkhum Channarong
Publication year - 2017
Publication title -
aquaculture research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.646
H-Index - 89
eISSN - 1365-2109
pISSN - 1355-557X
DOI - 10.1111/are.12917
Subject(s) - biology , lates , aquaculture , streptococcus iniae , perciformes , freshwater fish , gill , fish farming , barramundi , veterinary medicine , microbiology and biotechnology , fish <actinopterygii> , fishery , medicine
Asian seabass ( Lates calcarifer ) has been recognized as an economically important aquaculture species which can be adapted to and cultivated in wide range of salinities. The number of freshwater intensive seabass farms in Thailand is increasing annually. Here, we first describe the susceptibility of Asian seabass, which were cultured in freshwater, to Streptococcus inae ( SI ) and their pathological changes. Three isolates of putative SI were identified using a combination of standard biochemical assays and species‐specific PCR prior subjected to in vivo challenge. Accumulated mortalities of the fish which received 10 7 CFU fish −1 of either SI 1J, SI SGSA or SI 2J were 90%, 90% and 100% at 7 days‐post infection (dpi), respectively, and mortalities increased sharply between 3 and 5 dpi. Clinical signs such as erratic swimming and opaque eyes were identified from a few infected fish, while most died rapidly without any abnormal signs. Histopathological manifestations were observed in the multiple organs (kidney, liver and brain). Haemorrhage, hyperhemia, cellular degeneration and inflammatory cells infiltration were commonly found within the internal organs. Notably, the formation of numerous encyst‐like lesion aggregated by eosinophilic cells, resembling macrophages, were typically found in the brain of the infected fish. Summarily, this study first revealed that freshwater reared Asian seabass is highly susceptible to SI infection and haemorrhagic septicaemia was a major pathological change that could be found in the infected fish.