Complete Genome Sequencing of an Embryonated Chicken Egg-Adapted Duck atadenovirus A

Egg drop syndrome (EDS) is prevalent in industrial poultry globally. This disease is caused by Duck atadenovirus A or EDS virus (EDSV), a member of the genus Atadenovirus under the family Adenoviridae. The disease is attributed to significant economic losses in the poultry industry worldwide due to a drop in egg production, reduction in egg quality, and failure to reach maximum egg production. Oil‐adjuvant inactivated vaccines, which are widely used in the poultry industry, provide good protection for immunized chickens against EDS. This study aimed to genetically and phylogenetically analyze the full-length genome of an embryonated chicken egg-adapted EDSV strain ۱۲۷. After extraction of viral DNA from the allantoic fluid, overlapping fragments of the viral genome sequence were generated by polymerase chain reaction (PCR) using ۲۵ pairs of primers. Purified PCR products were subjected to complete genome sequencing by the next-generation sequencing (NGS) approach. The nucleotide homology observed between genomes of the studied strain and that of the original strain ۱۲۷ (NC_۰۰۱۸۱۳) of laying chickens was ۹۹.۹%. Its genome was ۳۳,۲۱۳ bp in length, with a G + C content of ۴۳.۰۱%. A comparison of the genome sequence of the egg-adapted virus with strain ۱۲۷ revealed only three non-synonymous single-nucleotide polymorphisms (SNPs) between these viral genome sequences. Two mutations of S۳۲۰G and I۶۲K out of these SNPs were found within the coding regions of fiber and hypothetical proteins which may play a role in the adaptation of EDSV in the embryonated chicken eggs. The full genome sequencing of EDSV using NGS techniques provides insights into the discovery of genetic variants. Moreover, the genome sequence information of the EDSV provides valuable data for vaccine development in near future.

Keywords:

Duck atadenovirus A , egg drop syndrome , egg-adapted virus , Molecular Characterization , Next Generation Sequencing