Isolation of a new rhabdovirus from cultured hirame (Japanese flounder, Paralichthys olivaceus) in Japan

In March 1984, a new rhabdovirus was isolated from moribund cultured hirame (Japanese, Paralichthys olivaceus) and from ayu (Plecoglossus altivelis) fry in Hyogo Prefecture. From February through May 1985, the virus was again isolated from hirame in seawater tanks in Hyogo and Kagawa Prefecture, and in Hokkaido, Japan. At temperatures between 5 and 20 deg C the virus replicated and induced cytophatic effects (CPE), which progressed to eventual cytolysis in susceptible cell lines, including FHM, EPC, BF-2, RTG-2, STE-137, HF-1BB, YNK, CCO and EK-1. The CHSE-214, K0-6 and CHH-1 cell lines were refractory. Maximum ineffectivity of cell culture-grown virus was about 10 to the nine point three power-10 to the nine point eight power TCD 50/ml in FHM cell lines. The virus replicated optimally at 15 to 20 deg C. Virus particles were bullet shaped, 80 nm x 180 to 200 nm. The isolate was sensitive to pH3, to diethyl ether, and to heat (50 deg C, 2 min). The virus did not hemagglutinate human O type erythrocytes. Viral replication was not inhabited by 10 to the negative fourth power M 5-iododeoxyuridine. Ineffectivity was not reduced by antisera against infectious hematopoietic virus (INHV), viral hemorrhagic septicemia virus (VHSV), spring viremia of carp virus (SVCV), pike fry rhabdovirus (PFRV), eel virus-American (EVA) and eel virus-European (EVX). The viral isolate was pathogenic for hirame and rainbow trout (Salmo gairdneri) by injection but not for chum salmon (Oncorhynchus keta), coho salmon (O. kisutch), masu salmon (O. masou), or ayu fry by water borne exposure. From the evidence obtained thus far, this virus is a new pathogenic virus of fish, and is provisionally named HRV (hirame rhabdivirus). HRV is now considered to be an important pathogen of cultured hirame and salmonids in Japan.