Mass Mortality of Cultured Sevenband Grouper, Epinephelus septemfasciatus, Associated with Viral Nervous Necrosis.

Abstract

Mass mortalities of sevenband grouper Epinephelus septemfasciatus reared in Oita Prefecture were investigated. The outbreaks of the disease occurred in summer seasons (July to October; water characterized by upside down swimming and inflation of swimbladder. Histopathologically, necrosis and vacuolation in the central nervous tissues and retina were observed. Although bacteria or parasites associated with the disease were not detected from affected fish and no CPE was observed on RTG-2, BF -2, and EPC cell lines, spherical virus particles, 28 nm in diameter, were found abundantly in the cytoplasm of affected nerve cells of most of the affected fish. The virus was identified as a fish nodavirus (nervous necrosis virus), based on the results of fluorescent antibody technique test with anti-SJNNV rabbit serum and polymerase chain reaction test with primers for amplification of SJNNV coat protein gene. These results suggest that the mortalities of sevenband grouper were at least partly due to viral nervous necrosis (VNN). This is the first report describing VNN of sevenband grouper and the first case of VNN in the adult fish.

Betanodavirus of Marine and Freshwater Fish: Distribution, Genomic Organization, Diagnosis and Control Measures

“…Larval or juvenile stages are more prone to this viral infection, but significant mortality can also occur in older fish up to production-size as in European seabass, sevenband grouper, humpback grouper Cromileptes altivelis and Atlantic halibut Hippoglossus hippoglossus [4,37,71,83,86,125]. Infections are also reported in freshwater fish, such as Chinese catfish (P. asotus); Australia catfish (Tandanus tandanus); Barramundi (L. calcarifer); Medaka (Oryzias latipes); guppy (Poicelia reticulata) and zebrafish (Danio rerio) [5,22,52,53,62,63,76].…”

“…Classical signs of disease are most commonly observed in larval and juvenile fishes since they are commonly affected [82] and sometimes in adult fish [37,71,103]. Diseased fish show various clinical symptoms which include reduced appetite, emaciation, colour change (darkening), abnormal (whirling) swimming pattern, neurological dysfunction, exophthalmia, swim bladder hyperinflation, floating belly up with inflation of swim bladder, anorexia and gas accumulation and extensive mortality ( Fig.…”

“…Diseased fish show various clinical symptoms which include reduced appetite, emaciation, colour change (darkening), abnormal (whirling) swimming pattern, neurological dysfunction, exophthalmia, swim bladder hyperinflation, floating belly up with inflation of swim bladder, anorexia and gas accumulation and extensive mortality ( Fig. 1) [6,37,38,49,64,77,85,97,102,117,126], (Shetty et al unpublished data). Gross lesions are uncommon, but overinflation of the swimbladder has been observed [37,92].…”

“…1) [6,37,38,49,64,77,85,97,102,117,126], (Shetty et al unpublished data). Gross lesions are uncommon, but overinflation of the swimbladder has been observed [37,92]. Several investigators have confirmed the presence of betanodavirus in fish without evidence of any disease signs as in brown meagre (Sciaena umbra) and Atlantic salmon (Salmo salar) [9,29,43,48].…”

Seasonal population dynamics of the monogeneans Pseudorhabdosynochus coioidesis and P. serrani on wild versus cultured groupers in Daya Bay, South China Sea

“…The outbreak of diseases has been an impediment to their culture (Zeng, 2006;Do & Phan, 2007). Deadly pathogens, including viruses, bacteria and parasites, have been reported (Fukuda et al, 1996;Leong, 1997;Cribb et al, 2002;Nagasawa & Cruz-Lacierda, 2004;Yuki et al, 2008). Monogeneans are a group of pathogens which are difficult to eradicate in an open culture system (Leong, 1997).…”