“…Considering that even striped jack has a strict age-dependent resistance against SJNNV (Arimoto et al, 1993), less susceptible Japanese jack mackerel might be more resistant at juvenile or older stages and thus possibly develop into subclinical infection. We previously reported that RNA2 determines the host-specificity of betanodaviruses (SJNNV and RGNNV) and the T4 region in RNA2 is particularly important for pathogenicity (Iwamoto et al, 2004;Ito et al, 2008). After the first report on SJNNV of striped jack larvae in 1992 (Mori et al, 1992), the SJNNV genotype was detected by cell culture isolation or PCR from cultured Senegalese sole Solea senegalensis, sea bass Dicentrarchus labrax, and gilthead sea bream Sparus aurata in southern Europe, and these European SJNNVs are phylogenetically different from Japanese SJNNVs all of which were isolated from diseased striped jack larvae (Thiéry et al, 2004;Cutrín et al, 2007;Toffolo et al, 2007;Olveira et al, 2009;Cherif et al, 2011;Panzarin et al, 2012).…”