Molecular characterization and phylogenetic analysis of fowl adenovirus serotype-4 from Guangdong Province, China.

Aim: Our aim in this study was to isolate potentially novel strains of fowl adenovirus serotype-4 (FAdV-4) that is currently circulating in broiler chicken flocks in Guangdong Province, China, and to compare nucleotide and amino acid (AA) sequences of their respective hexon genes. Materials and Methods: The experiment was carried out on poultry farms experiencing outbreaks of FAdV-4-associated hydropericardium syndrome (HPS). Tissue samples from the hearts and livers of deceased chickens were screened for FAdV-4 infection using hexon gene-specific polymerase chain reaction (PCR). Results: New virus isolates were used to infect 7-day-old chicks, which went onto reproduce typical HPS signs. The hypervariable region of the FAdV-4 hexon gene was PCR-amplified and sequenced. The hexon nucleotide and deduced AA sequence identities were 99.8-99.9% and 99.5-99.8%, respectively, among the four novel isolates. In addition, the new isolates were 97-100% and 96.4-99.9% identical to the nucleotide and deduced AA sequences, respectively, of FAdV-4 hexon genes available in the National Center for Biotechnology Information GenBank database. Phylogenetic analyses, based on the hexon gene sequence, revealed that the new isolates, clustered with FAdV-C; the FAdV-A, FAdV-B, FAdV-D, and FAdV-E viruses, were more distantly related. Conclusion: New FAdV-4 isolates from Guangdong Province are similar to those identified in other regions of the world. This information provides critical insight into HPS epidemiology and provides a perspective for monitoring outbreaks and developing strategies for disease prevention.