Complete genome sequencing, molecular and antigenic characterization of duck hepatitis A virus type 1 isolated in...

Duck virus hepatitis (DVH) is highly fatal disease that predominantly affects young ducklings, causing substantial losses due to its high morbidity and mortality rates. A severe outbreak occurred in young Pekin ducklings on a commercial farm in Benha, Egypt.

The affected birds exhibited neurological signs, including lethargy, ataxia, and opisthotonus, leading to a high mortality rate. The livers and kidneys of ducklings showed various degrees of gross and histopathological lesions. Virus isolation trials in embryonated duck eggs revealed the characteristic greenish discoloration of the allantoic fluid, along with hepatitis and embryonic mortality. Furthermore, RT-PCR confirmed the presence of suspected duck hepatitis A virus type 1(DHAV-1). This study presents the first complete genome sequence of DHAV-1 from Egypt using next generation sequencing (NGS). Sequence analysis revealed that DHAV-1 exhibits the characteristic genomic organization of Avihepatovirus. The whole nucleotide sequence of Du/Egy/Benha/2020/DHAV-1 showed a high similarity to viruses isolated from Hungary in 2004, with a 99.9% identity in both the complete genome and structural genes (VP0, VP3, VP1). Antigenic analysis revealed a unique escape mutation, S178Y, related to conserved antigenic determinants on VP1 of DHAV-1 isolate. The cross-neutralization assay was utilized to assess the antigenic diversity between the field strain and the locally used live attenuated vaccine strain.

The results revealed minimal antigenic variation, highlighting the potential for immune evasion. These findings suggest that the currently administered vaccines in Egypt remain effective in controlling DHAV-1 infections. However, continuous surveillance is essential to monitor any emerging genetic or antigenic changes that could compromise vaccine efficacy in the future.