The enteric virus associated with baby chick nephropathy in Japan was genetically identified as chicken astrovirus, not avian nephritis virus.

Abstract

In Japan, avian nephritis virus (ANV) isolates associated with the 1989 outbreak of baby chick nephropathy (BCN) were previously reported as pathologically and serologically distinct from known ANV strains. However, genetic analysis conducted in this study revealed that these viruses were actually chicken astrovirus (CAstV), first described in 2004, and genetically distinct from ANV. Phylogenetic analysis based on the open reading frame 2 (ORF2) gene, which encodes the viral capsid protein, classified this virus within the subgroup Bi, along with isolates from Saga Prefecture in 2020 which were the only CAstV reported in Japan to date. These findings suggest that CAstV was already present in Japan in the 1980s, predating its first global report in 2004 and its first domestic report.