Genome characterization and environmental DNA-based detection of a novel adenovirus from red seabream (Pagrus major).

A novel piscine adenovirus, Pagrus major adenovirus 1 (PmAdV-1), was identified in red seabream (Pagrus major) by metagenomic sequencing. The 29,519 bp genome encodes 22 predicted open reading frames and exhibits a unique organization, with the fiber gene positioned upstream of the conserved adenovirus gene cluster. Phylogenetic analyses indicate that PmAdV-1 forms a sister lineage to red-eared slider adenovirus 1 within a clade of fish and reptilian adenoviruses, but its assignment to the genus Testadenovirus remains uncertain. A virus-specific qPCR assay was developed to monitor PmAdV-1 in environmental DNA from rearing seawater. Viral loads transiently increased in some juvenile tanks without marked mortality. These findings expand current knowledge of fish adenovirus diversity.