Phylogenetic and pathogenic characterization of current fowl adenoviruses in China

In recent years, fowl adenoviruses (FAdVs) continue to outbreak and cause huge economic losses to the poultry industry in China. The homologous recombination accounts for the diversity serotypes of adenovirus. However, the prevalence, recombination and pathogenicity of current FAdVs remain unclear. Herein, the prevalence, phylogenetic feature and pathogenicity of FAdVs in China in 2019 were characterized. Our findings showed that multiple species and serotypes of FAdVs currently circulate in China, including A, C, D and E species, and 1, 2, 4, 8a and 8b serotypes. Notably, the recombination occurred between FAdV-8a and FAdV-8b, and the recombination regions included Hexon, Fiber, ORF19 and ORF20. All five FAdVs replicated effectively in various chicken tissues, and viral shedding peaked at 4–8 dpi. Except CH/GDSZ/1905(FAdV-1/A), the remaining FAdVs caused obvious inclusion body hepatitis (IBH) in 3-week-old specific-pathogen-free (SPF) chickens, of which CH/JSXZ/1905(FAdV-4/C) caused hydropericardium-hepatitis syndrome (HHS) with a mortality rate of 62.5%. Taken together, our findings illustrate the prevalence, recombination and pathogenicity of current FAdVs in China and strengthen surveillance and further pathogenicity studies of FAdVs are extremely urgent. •Multiple species and serotypes of FAdVs circulate in different poultry flocks in china, including A, C, D and E species, and 1, 2, 4, 8a and 8b serotypes. FAdV-4 exhibits highly pathogenic to chicken with a mortality of 62.5%.•The homologous recombination accounts for the diversity serotypes of adenovirus. In this study, the recombination occurred between isolated FAdV-8a and FAdV-8b strains, and the recombination regions included Hexon, Fiber, ORF19 and ORF20.•Recombinant FAdV-8a and FAdV-8b strains caused obvious inclusion body hepatitis (IBH) in 3-week-old SPF chickens, and replicated effectively in various chicken tissues and viral shedding peaked at 4–8 dpi.