Isolation of a rhabdovirus during outbreaks of disease in cyprinid fish species at fishery sitesin England

[摘要] ABSTRACT: A virus was isolated during disease outbreaks in bream Abramis brama, tench Tinca tinca, roach Rutilis rutilis and crucian carp Carassius carassius populations at 6 fishery sites in England in 1999. Mortalities at thesites were primarily among recently introduced fish and the predominant fish species affected was bream. The bream stocked at 5 of the 6 English fishery sites were found to have originated from the River Bann, Northern Ireland. Most fish presented fewconsistent external signs of disease but some exhibited clinical signs similar to those of spring viraemia of carp (SVC), with extensive skin haemorrhages, ulceration on the flanks and internal signs including ascites and petechial haemorrhages. The mostprominent histopathological changes were hepatocellular necrosis, interstitial nephritis and splenitis. The virus induced a cytopathic effect in tissue cultures (Epithelioma papulosum cyprini [EPC] cells) at 20°C and produced moderate signals in anenzyme immunoassay (EIA) for the detection of SVC virus. The virus showed a close serological relationship to pike fry rhabdovirus in both EIA and serum neutralisation assays and to a rhabdovirus isolated during a disease outbreak in a bream populationin the River Bann in 1998. A high degree of sequence similarity (≥99.5% nucleotide identity) was observed between the English isolates and those from the River Bann. Experimental infection of juvenile bream, tench and carp with EPC cell-grown rhabdovirby bath and intraperitoneal injection resulted in a 40% mortality of bream in the injection group only. The virus was re-isolated from pooled kidney, liver and spleen tissue samples from moribund bream. The field observations together with theexperimental results indicate that this rhabdovirus is of low virulence but may have the potential to cause significant mortality in fishes under stress.

[学科分类] 生物科学（综合）

[关键词] Fish;Rhabdovirus;Cyprinids;Histopathology;Enzyme immunoassay;RT-PCR