Temporal Change In Genetical Lineages Of Infectious Hematopoietic Necrosis Virus (Ihnv) In The North Kanto Region Of Japan From 1981 To 2015

We analyzed the full-length glycoprotein gene sequences of 72 infectious hematopoietic necrosis virus (IHNV) isolates that had been obtained from diseased salmonid fish in the North Kanto region of Japan from 1981 through 2015. The analysis identified three genetical lineages in the genogroup J of IHNV; two known Shizuoka (JS) and Nagano (JN) lineages and a new lineage named as North Kanto lineage (Jnk). Most of the isolates from the 1980s were classified into JS lineage, whereas most collected after 2000 belonged to JN lineage. Jnk lineage was classified into North Kanto A clade [Jnk-A] and B Glade [Jnk-B], and the number of isolates belonging to Jnk-B in the 2010s was higher than in the 2000s. These results suggest that the diversity of IHNV found in salmonid farms in the North Kanto region have been increasing with genetical lineage shifting from 1980 to the present, probably due to change of the fish trade.