Genomic Epidemiology and Evolution of Fowl Adenovirus 1

SIMPLE SUMMARY: Gizzard erosion is an important pathology in chickens. Aviadenoviruses, in particular, fowl adenovirus 1, have been associated with the etiology of gizzard erosion. Clinical and pathology data from the field and from infection experiments suggested that both virulent and avirulent strains are circulating, although the genetic differences between these two FAdV-1 pathotypes have not been clarified. In this study, we analyzed a total of 40 FAdV-1 genomes, including 32 newly determined genome sequences, and demonstrated that a set of viral genes differ phylogenetically between the two pathotypes. These findings may help select suitable naturally attenuated FAdV-1 strains that can be used as an effective live vaccine acting directly on the mucosal surface of the gizzard. ABSTRACT: Fowl adenovirus 1 (FAdV-1) is the main cause of gizzard erosion in chickens. Whole genome sequencing and sequence analyses of 32 FAdV-1 strains from a global collection provided evidence that multiple recombination events have occurred along the entire genome. In gene-wise phylogenies, only the adenoviral pol gene formed a tree topology that corresponded to whole genome-based phylogeny. Virus genetic features that were clearly connected to gizzard erosion were not identified in our analyses. However, some genome variants tended to be more frequently identified from birds with gizzard erosion and strains isolated from healthy birds or birds with non-specific pathologies tended to form common clusters in multiple gene phylogenies. Our data show that the genetic diversity is greater, and the evolutionary mechanisms are more complex within FAdV-1 than previously thought. The implications of these findings for viral pathogenesis and epidemiology await further investigation.