Prevalence, genomic characteristics, and pathogenicity of fowl adenovirus 2 in Southern China

In recent years, the occurrence of fowl adenovirus 2 (FAdV-2) has been on the rise in China, posing a significant threat to the poultry industry. This study aimed to investigate the epidemiology, phylogenetic relationship, genomic characteristics, and pathogenicity of FAdV-2. The epidemiological analysis revealed the detection of multiple FAdV serotypes, including FAdV-1, FAdV-2, FAdV-3, FAdV-4, FAdV-8a, FAdV-8b, and FAdV-11 serotypes. Among them, FAdV-2 exhibited the highest proportion, accounting for 21.05% (8/38). The complete genomes of these 8 FAdV-2 strains were sequenced. Genetic evolution analysis indicated that these FAdV-2 strains formed a separate branch within the FAdV-D group, sharing 94.60 to 97.90% nucleotide similarity with the reference FAdV-2 and FAdV-11 strains. Notably, the recombination analysis revealed that 5 out of the 8 FAdV-2 strains, exhibited recombination events between FAdV-2 and FAdV-11. The recombination regions involved Hexon, Fiber, ORF19 genes and 30 end. Furthermore, pathogenicity experiments demonstrated that recombinant FAdV-2 XX strain is capable of inducing mortality rate of 66.70% and causing more severe hepatitis hydropericardium syndrome (HHS) in 6-wk-old specific-pathogen-free chickens. These findings contribute to our under-standing of the prevalence, genomic characteristics, and the pathogenicity of FAdV-2, providing foundations for FAdV-2 vaccine development.

Automated summary

In recent years, there has been an increase in the occurrence of fowl adenovirus 2 (FAdV-2) in China, posing a significant threat to the poultry industry. This study investigated the epidemiology, phylogenetic relationship, genomic characteristics, and pathogenicity of FAdV-2. The results showed that FAdV-2 was the most commonly detected serotype among various FAdV serotypes. Genetic analysis revealed that these FAdV-2 strains formed a distinct branch within the FAdV-D group and had a high nucleotide similarity with reference strains. Recombination analysis identified recombination events between FAdV-2 and FAdV-11 in some strains. Pathogenicity experiments demonstrated that a recombinant FAdV-2 strain caused a high mortality rate and more severe disease in chickens. These findings contribute to our understanding of FAdV-2 and provide a basis for vaccine development.