Isolation and identification of infectious salmon anaemia virus (ISAV) from Coho salmon in Chile

Abstract

The isolation of infectious salmon anaemia virus (ISAV) from asymptomatic wild fish species including wild salmon, sea trout and eel established that wild fish can be a reservoir of ISAV for farmed Atlantic salmon. This report characterizes the biological properties of ISAV isolated from a disease outbreak in farmed Coho salmon in Chile and compares it with ISAV isolated from farmed Atlantic salmon in Canada and Europe. The virus that was isolated from Coho salmon tissues was initially detected with ISAV-specific RT-PCR (reverse transcription-polymerase chain reaction). The ability of the virus to grow in cell culture was poor, as cytopathology was not always conspicuous and isolation required passage in the presence of trypsin. Virus replication in cell culture was detected by RT-PCR and IFAT (indirect fluorescent antibody test), and the virus morphology was confirmed by positive staining electron microscopy. Further analysis of the Chilean virus revealed similarities to Canadian ISAV isolates in their ability to grow in the CHSE-214 cell line and in viral protein profile. Sequence analysis of genome segment 2, which encodes the viral RNA polymerase PB1, and segment 8, which encodes the nonstructural proteins NS1 and NS2, showed the Chilean virus to be very similar to Canadian strains of ISAV. This high sequence similarity of ISAV strains of geographically distinct origins illustrates the highly conserved nature of ISAV proteins PB1, NS1 and NS2 of ISAV. It is noteworthy that ISAV was associated with disease outbreaks in farmed Coho salmon in Chile without corresponding clinical disease in farmed Atlantic salmon. This outbreak, which produced high mortality in Coho salmon due to ISAV, is unique and may represent the introduction of the virus to a native wild fish population or a new strain of ISAV. KEY WORDS: ISAV in Coho salmon · ISAV morphology · Immunoprecipitation of ISAV proteins Resale or republication not permitted without written consent of the publisherDis Aquat Org 45: [9][10][11][12][13][14][15][16][17][18] 2001 associated, resulting in focalized infection of the cell monolayer and slow development of CPE. ISAV isolates from Norway and Scotland, similar to the second Canadian group (the CHSE-negative phenotype), do not produce CPE in the CHSE-214 cell line. However, there are significant nucleotide and amino acid sequence differences between the European and Canadian isolates on RNA segments 2 and 8 (Blake et al. 1999), and the European isolates could be differentiated from Canadian isolates by reverse transcriptionpolymerase chain reaction (RT-PCR) and restriction fragment length polymorphism (RFLP) on RNA segment 2 (Kibenge et al. 2000).The present study characterizes an orthomyxo-like virus isolated from farmed Coho salmon Oncorhynchus kisutch in Chile, with clinical disease. While erythrocytic inclusion body syndrome virus (EIBSV) was detected in one fish sample, the orthomyxo-like virus was found in several fish tissue pools from the affected farms. The virus was biologically chara...

Experimental infection models and susceptibility of Atlantic salmon Salmo salar to a Scottish isolate of infectious salmon anaemia virus

“…Although epizootics have occurred in Norway since 1984, the disease has only recently been diagnosed in Canada (Mullins et al 1998, Bouchard et al 1999, Lovely et al 1999, Scotland (Rodger et al 1998, Stagg et al 1999, Turnbull 1999, Chile (Kibenge et al 2001), Faroes (Anonymous 2000) and the USA (Bouchard et al 2001). Typical pathological changes are severe anaemia, leucopenia, ascites and haemorrhagic liver necrosis (Thorud & Djupvik 1988, Evensen et al 1991.…”

Caligus rogercresseyi: posible vector en la transmision horizontal del virus de la anemia infecciosa del salmon (ISAv)

“…El primer brote de virus ISA se registró en Noruega en 1984 (Thorud & Djupvik, 1988) y desde entonces la enfermedad se ha registrado en todos los principales países productores de salmón del Atlántico: Canadá (Mullins et al, 1998;Ritchie et al, 2001), Escocia (Rodger et al, 1998;Rowley et al, 1999), Estados Unidos (Maine) (Bouchard et al, 2001), Islas Faroe (Lyngøy, 2003) y Chile (Kibenge et al, 2001;Godoy et al, 2008). La especie más susceptible es el salmón del Atlántico (S. salar), pero también logra sobrevivir e infectar a la trucha de mar (Salmo trutta), trucha arcoiris (Onchorhynchus mykiss) y salmon coho (O. kisutch) (Kibenge et al, 2001), los cuales no manifiestan la enfermedad pero pueden actuar como vectores y reservorios del virus ISA (Nylund et al, 1995Hastein, 1997;Rolland & Nylund, 1998).…”

“…La especie más susceptible es el salmón del Atlántico (S. salar), pero también logra sobrevivir e infectar a la trucha de mar (Salmo trutta), trucha arcoiris (Onchorhynchus mykiss) y salmon coho (O. kisutch) (Kibenge et al, 2001), los cuales no manifiestan la enfermedad pero pueden actuar como vectores y reservorios del virus ISA (Nylund et al, 1995Hastein, 1997;Rolland & Nylund, 1998).…”

Completion of the full-length genome sequence of the infectious salmon anemia virus, an aquatic orthomyxovirus-like, and characterization of mAbs

“…Although, ISA virus (ISAV) outbreaks were observed only in Atlantic salmon, the virus was detected from apparently healthy animals in other species (Raynard et al, 2001). The only exception was the isolation of ISAV from diseased Coho salmon (Oncorhynchus kisutch) in Chile in 1999 (Kibenge et al, 2001). Experimental infections showed that other species could be susceptible to ISAV infection, especially juvenile rainbow trout (Oncorhynchus mykiss) for which mortality was recorded after both virus injection and bath immersion, which may represent a threat to the trout industry (Biacchesi et al, 2007).…”