Characterization of perch rhabdovirus (PRV) in farmed grayling Thymallus thymallus

Abstract

Two Finnish fish farms experienced elevated mortality rates in farmed grayling Thymallus thymallus fry during the summer months, most typically in July. The mortalities occurred during several years and were connected with a few neurological disorders and peritonitis. Virological investigation detected an infection with an unknown rhabdovirus. Based on the entire glycoprotein (G) and partial RNA polymerase (L) gene sequences, the virus was classified as a perch rhabdovirus (PRV). Pairwise comparisons of the G and L gene regions of grayling isolates revealed that all isolates were very closely related, with 99 to 100% nucleotide identity, which suggests the same origin of infection. Phylogenetic analysis demonstrated that they were closely related to the strain isolated from perch Perca fluviatilis and sea trout Salmo trutta trutta caught from the Baltic Sea. The entire G gene sequences revealed that all Finnish grayling isolates, and both the perch and sea trout isolates, were most closely related to a PRV isolated in France in 2004. According to the partial L gene sequences, all of the Finnish grayling isolates were most closely related to the Danish isolate DK5533 from pike. The genetic analysis of entire G gene and partial L gene sequences showed that the Finnish brown trout isolate ka907_87 shared only approximately 67 and 78% identity, respectively, with our grayling isolates. The grayling isolates were also analysed by an immunofluorescence antibody test. This is the first report of a PRV causing disease in grayling in Finland.

Emergence of a new rhabdovirus associated with mass mortalities in eelpout (Zoarces viviparous) in the Baltic Sea

“…Several piscine rhabdoviruses have been described to cause serious disease, among those viral haemorrhagic septicaemia virus (VHSV), infectious haematopoietic necrosis virus (IHNV) and spring viremia of carp virus (SVCV), and rhabdoviruses have serious socio‐economic impact in fish (Gadd et al . ; Ma et al . ; Zhu & Zhang ).…”

“…Rhabdoviruses are encapsulated negative-sense single-stranded RNA viruses that cause disease in a wide range of animals (Lyles, Kuzmin & Rupprecht 2013). Several piscine rhabdoviruses have been described to cause serious disease, among those viral haemorrhagic septicaemia virus (VHSV), infectious haematopoietic necrosis virus (IHNV) and spring viremia of carp virus (SVCV), and rhabdoviruses have serious socio-economic impact in fish (Gadd et al 2013;Ma et al 2013;Zhu & Zhang 2014).…”

Mortality outbreak by perch rhabdovirus in European perch (Perca fluviatilis) farmed in Italy: Clinical presentation and phylogenetic analysis

“…Outbreaks of PRV infection were also reported in Denmark, Ireland, Germany, Norway and Switzerland (Bigarré et al, ; Dannevig et al, ; Dorson et al, ; Jørgensen, Olesen, Ahne, Wahli, & Meier, ; Wahli et al, ). More recently, PRV was detected for the first time in Finland in grayling fry ( Thymallus thymallus L.) (Gadd, Viljamaa‐Dirks, Holopainen, Koski, & Jakava‐Viljanen, ).…”

“…PCR products were visualized by gel electrophoresis and sequenced with both the forward and reverse PCR primers using ABI PRISM Big Dye Terminator v.3.1 cycle sequencing kit. Subsequently, for phylogenetic analysis, primers pairs oPVP116 and oPVP118 (Talbi et al, ), and oPVP126 (Talbi et al, ) and Rha‐G‐seqR2 (Gadd et al, ) were used to obtain the complete viral G gene sequence in two overlapping fragments. The expected amplicon size for primers oPVP116&oPVP118 was approximately 1,400 bp, while for primers oPVP126&Rha‐G‐seqR2 was 676 bp.…”

“…Phylogenetic analysis (Figure ) based on the complete sequence of the glycoprotein G gene (1.560 nts) revealed that our isolate clusters into genogroup B, which includes other PRV isolates from Perca fluviatilis identified in France (2004–2009) that share 98.6%–99.2% similarity with our sequence at the glycoprotein G gene. Genogroup B also includes one isolate from the Baltic Sea and PRV sequences 196 identified in other host species, like Salmo trutta L. (Baltic Sea, 2009) and Thymallus thymallus (Finland, 2002–2010) (Gadd et al, ). However, all these sequences have relatively lower similarities (95.3%–96.9%).…”