Molecular Characterization of Fowl Adenovirus from Brazilian Poultry Farms

Fowl adenovirus (FAdV) can cause different poultry diseases with economic losses in the broilers and layers commercial farms. FAdV is currently classified into five species and 12 serotypes, disseminated in poultry flocks worldwide. The present study aimed to identify FAdV species and serotypes in Brazilian poultry farms. A total of 678 chicken flocks from the main Brazilian poultry-producing regions were evaluated for FAdV infection between 2020 and 2023. FAdV was detected by a real-time PCR targeting 52K gene and further genotyped by partial sequencing of the hexon gene followed by phylogenetic analyses. The results demonstrated that FAdV was detected in 72 flocks (10.6%). In 46 of these samples, FAdV species and serotypes could be identified, including three main species: Aviadenovirus ventriculi (FAdV-A = 15), Aviadenovirus gallinae (FAdV-D = 15) and Aviadenovirus hepatitidis (FAdV-E = 16). Phylogenetic analysis based on 173 partial hexon sequences (including sequences from this study, 44 previously sequenced in Brazil, and 86 data from other countries) revealed five separate clades for FAdV species. All Brazilian FAdVs were classified into the same three species reported above (FAdV-A = 19, FAdV-D = 34, FAdV-E = 37), and also in well-supported subclades for each serotype: FAdV-A1 (n = 19), FAdV-D9 (n = 1), FAdV-D11 (n = 33), FAdV-E6 (n = 1), FAdV-E8a (n = 33), FAdV-E8b (n = 3). Amino acid substitutions in the hyper variable regions (1, 2 and 3) and conserved motifs of the Hexon protein were further analyzed, enabling discrimination between closely related serotypes. This study demonstrates the circulation of different FAdVs in Brazil, highlighting FAdV-A1, FAdV-D9, FAdV-D11, FAdV-E6, FAdV-E8a and FAdV-E8b. The findings reported here also indicate genetic and amino acid diversity in the Hexon protein of the FAdVs in Brazilian poultry farms, which are of importance for molecular surveillance and poultry diseases control strategies.