Screening for Viral Hemorrhagic Septicemia Virus in Marine Fish along the Norwegian Coastal Line

Fish rhabdoviruses are a family of viruses responsible for large‐scale fish die‐offs worldwide. Here, we reported the isolation and identification of a member of rhabdoviruses from wild largemouth bass (Micropterus salmoides) in the coastal area of the Pearl River Estuary, China. This virus isolate was identified as viral haemorrhagic septicaemia virus (VHSV) by specific RT‐PCR. Furthermore, the virus (VHSVLB2018) was isolated by cell culture using fathead minnow cells and confirmed by RT‐PCR. Electron microscopy showed the presence of bullet‐shaped viral particles in the cytoplasm of infected cells. The complete sequencing of VHSVLB2018 confirmed that it was genome configuration typical of rhabdoviruses. Phylogenetic analysis based on whole‐genome sequences and G gene nucleotides sequences revealed that VHSVLB2018 was assigned to VHSV genogroup Ⅳa. The pathogenicity of VHSVLB2018 was determined in infection experiments using specific pathogen‐free largemouth bass juveniles. VHSVLB2018‐infected fish showed typical clinical signs of VHSV disease, including darkened skin, petechial haemorrhages and pale enlarged livers, with the cumulative mortalities reached 63.3%–93.3% by 7 days post‐infection. VHSVLB2018 was re‐isolated from dead fish and confirmed by RT‐PCR. Together, this is the first report of isolation and identification of a VHSV isolate from wild largemouth bass in China.

Section: Discussionmentioning

confidence: 99%

Isolation and identification of a viral haemorrhagic septicaemia virus (VHSV) isolate from wild largemouth bass Micropterus salmoides in China

Zhang

Xiang

et al. 2019

“…Several RT-qPCR assays are available to detect the IHNV or VHSV genome (Cutrín et al, 2009;Garver et al, 2011;Gjevre, Ørpetveit, Tavornpanich, & Lyngstad, 2014;Hope et al, 2010;Jonstrup et al, 2013;Liu et al, 2008;Lopez-Vazquez, Bandín, & Dopazo, 2015;Phelps, Patnayak, Jiang, & Goyal, 2012;Pierce et al, 2013;Purcell et al, 2013;Sandlund et al, 2014;Warg et al, 2014aWarg et al, , 2014b. However, diagnostic performance of most IHNV and VHSV RT-qPCR assays has not been fully evaluated in accordance with OIE guidelines (Bustin et al, 2009;Jonstrup et al, 2013;OIE, 2017d;Warg et al, 2014a).…”

Section: Discussionmentioning

confidence: 99%

Improvement of a diagnostic procedure in surveillance of the listed fish diseases IHN and VHS

Hoferer

Akimkin

Skrypski

et al. 2019

Infectious haematopoietic necrosis (IHN) and viral haemorrhagic septicaemia (VHS) are OIE‐listed and notifiable viral fish diseases which are controlled by eradication and surveillance programmes globally. The present study provides improved RT‐qPCR procedures based on recently described OIE protocols. Improvements comprise the design of a new TaqMan® probe, replacing a TaqMan® MGB probe that turned out to show impaired binding. Reason for this is SNPs detected in the nucleoprotein N gene sequences of IHNV strains targeted by the RT‐qPCR. Furthermore, the IHNV and VHSV RT‐qPCR assays were realized as one‐step and one‐run procedures supplemented by an endogenous control system. The IHNV and VHSV RT‐qPCR assays are characterized by a technical sensitivity of 19 and 190 gene equivalents (cRNA) and an analytical sensitivity of 2–7 and 13 TCID50/ml, respectively. For verification purposes, 105 IHNV and 165 VHSV isolates and several non‐targeted viral and bacterial pathogens were included and returned adequate results. However, in field samples divergent results left 14 samples of 154 undetected for IHNV and one sample of 127 for VHSV using cell culture. The study shows that RT‐qPCR assays ensure facilitated and reliable testing on IHNV and VHSV in eradication and surveillance programmes.

“…This indicates that testing gills might detect more positive samples than testing internal organs. However, it has to be acknowledged that positive gills may either reflect true infection or virus being passively carried in the gill mucus (Sandlund et al., ) and hence are not suitable for diagnostic purposes.…”

Section: Discussionmentioning

confidence: 99%

Outbreak of viral haemorrhagic septicaemia (VHS) in lumpfish (Cyclopterus lumpus) in Iceland caused by VHS virus genotype IV

Guðmundsdóttir

Vendramin

Cuenca

et al. 2018

Self Cite

A novel viral haemorrhagic septicaemia virus (VHSV) of genotype IV was isolated from wild lumpfish (Cyclopterus lumpus), brought to a land‐based farm in Iceland, to serve as broodfish. Two groups of lumpfish juveniles, kept in tanks in the same facility, got infected. The virus isolated was identified as VHSV by ELISA and real‐time RT‐PCR. Phylogenetic analysis, based on the glycoprotein (G) gene sequences, may indicate a novel subgroup of VHSV genotype IV. In controlled laboratory exposure studies with this new isolate, there was 3% survival in the I.P. injection challenged group while there was 90% survival in the immersion group. VHSV was not re‐isolated from fish challenged by immersion. In a cohabitation trial, lumpfish infected I.P. (shedders) were placed in tanks with naïve lumpfish as well as naïve Atlantic salmon (Salmo salar L.). 10% of the lumpfish shedders and 43%–50% of the cohabiting lumpfish survived after 4 weeks. 80%–92% of the Atlantic salmon survived, but no viral RNA was detected by real‐time RT‐PCR nor VHSV was isolated from Atlantic salmon. This is the first isolation of a notifiable virus in Iceland and the first report of VHSV of genotype IV in European waters.