Pathogenicity and complete genome sequence of a fowl adenovirus serotype 8b isolate from China

In this study, we determined and analyzed the complete nucleotide sequence of the genome of a fowl adenovirus isolate SD1356 in China and examined its pathogenicity in specific pathogen-free chick embryos and newly hatched chicks. The full genome of SD1356 was 44,454 nucleotides in length with 58.1% G + C content. Sequence alignment and phylogenetic analysis revealed that strain SD1356 was clustered together belonging to serotype 8b of fowl adenoviruses E species (FAdV-8b). No regions homologous to early regions E1, E3, and E4 of mastadenoviruses were recognized, and being very similar to the typical organization of FAdV-E genomes. All infected embryos died 4-6 d post-inoculation with visible lesions, such as hyperemic, stunting, and clubbed down, etc. Additionally, adenovirus was found in tissues or cloacal swabs of all infected birds and most of the contact uninfected controls, despite lack of clinical signs and pathological changes. Together, our study describes the genomic characteristics of an FAdV-8b strain isolated in China. The reported FAdV-8b strain SD1356 is fetal to chick embryos and possesses horizontal transmission capacity in chickens.