Analysis of the complete genomic sequence of an apparently avirulent strain of avian hepatitis E virus (avian HEV) identified major genetic differences compared with the prototype pathogenic strain of avian HEV.

Avian hepatitis E virus (HEV) was identified from chickens with hepatitis-splenomegaly syndrome. In this study, the complete genomic sequence of an apparently avirulent strain of avian HEV was determined to be 6649 nt in length, excluding the poly(A) tail, which is 5 nt shorter than the prototype avian HEV. Sequence analyses revealed that the ORF1 has 89.6% nucleotide sequence identity, with numerous non-silent mutations and deletions, compared to the prototype strain. The ORF2 capsid gene showed 90.7% sequence identity with six non-silent mutations, and ORF3 had four non-silent mutations with 97% sequence identity. Overall, the apparently avirulent strain shares only 90.1% nucleotide sequence identity with the prototype strain. The identification of significant non-silent mutations in the capsid gene and other regions suggests that these mutations may play a role in HEV attenuation. This is the first report of the full-length sequence of an apparently avirulent strain of HEV.