Nucleotide diversity of Japanese isolates of infectious hematopoietic necrosis virus (IHNV) based on the glycoprotein gene

Abstract

Infectious hematopoietic necrosis virus (IHNV), a member of the genus Novirhabdovirus, causes a highly lethal disease of salmonid fish. In the present study, G gene nucleotide sequences of 9 Japanese IHNV isolates obtained from 1971 to 1996 were analyzed to evaluate the genetic diversity and compared with IHNV isolates from North America and Europe. A radial phylogenetic tree revealed 5 major clusters including 3 genogroups (U, M and L) for North American isolates and 1 genogroup for European isolates. Five Japanese isolates from 1971 to 1982 appeared in the cluster for genogroup U, while the remaining Japanese isolates from 1980 to 1996 formed a new genogroup, JRt (Japanese rainbow trout). Maximum nucleotide diversity among the Japanese isolates was 4.5%, which was greater than that within the North American isolates (3.6%), and the degree of nucleotide diversity within Japanese isolates was increased by inclusion of the genogroup JRt isolates. It was concluded that Japanese isolates shared a common source with the genogroup U of the North American isolates and that there were large divergences between Japanese isolates before and after the 1980s.

Genotyping of Korean isolates of infectious hematopoietic necrosis virus (IHNV) based on the glycoprotein gene

“…The genogroup U includes isolates from Alaska, British Columbia, Washington coastal watersheds and the Columbia River basin; the genogroup M includes isolates from the Columbia River basin and Idaho; and the genogroup L includes isolates from California and the southern Oregon coast. More recently, two additional genogroups for European and Japanese isolates were identified [1,11]. It is interesting that the genogroup for European isolates shared a common source with the American genogroup M [1], while the genogroup for Japanese isolates was closely related with the American genogroup U [11].…”

“…The IHNV genome is a non-segmented and single-stranded negative-sense RNA with approximately 11,000 nucleotides containing six genes in the order 3'-N-P-M-G-NV-L-5' encoding the nucleocapsid protein (N), phosphoprotein (P), matrix protein (M), glycoprotein (G), non-virion protein (NV) and polymerase (L) genes, respectively [6,9]. The G, N and NV genes have been used for analyses of IHNV evolution, diversity and phylogenetic relationship among the worldwide isolates [1,3,7,10,11,16,17].…”

Detection of Specific Antibodies against Infectious Hematopoietic Necrosis Virus from Rainbow Trout Sera by ELISA using Two Novirhabdoviruses

“…The introduced IHNV was spread throughout wide areas of Japan in the 1970s, and then adapted and evolved in rainbow trout O. mykiss farm environments (Nishizawa et al, 2006). Moreover, parts of the evolved IHNV isolates in Japan were transported to Korea (Nishizawa et al, 2006;Kim et al, 2007a). In general, pathogenicity of IHNV has a bias toward alevin to fry.…”

“…IHN is originally enzootic in sockeye salmon Oncorhynchus nerka in the Pacific Northwest of North America, but it was spread to Asian and European countries by transportation of IHNV-contaminated fish eggs (Winton, 1991;Bootland and Leong, 1999). The introduced IHNV was spread throughout wide areas of Japan in the 1970s, and then adapted and evolved in rainbow trout O. mykiss farm environments (Nishizawa et al, 2006). Moreover, parts of the evolved IHNV isolates in Japan were transported to Korea (Nishizawa et al, 2006;Kim et al, 2007a).…”

“…However, in recent years significant mortalities by IHN have occurred in juvenile and marketable grown-up fish of rainbow trout. Under the circumstance on the epidemiology of IHNV in Japan, it was interested in how the evolutionary divergence influences viral pathogenicity (Nishizawa et al, 2006).…”