Molecular Characterization Reveals Recombination and Host Exchange of Adenoviruses in Migratory Birds in China

Migratory birds, because of their migration and roosting characteristics, can serve as major vectors for long-distance transmission, recombination, and evolution of adenoviruses. China is one of the countries possessing the widest variety of birds in the world, with the global migration routes covering almost the entire territory. However, avian adenoviruses haven't been systematically studied. In the current study, PCR-based molecular methods were used to characterize the adenoviruses in 38 migratory bird species from nine provinces in China from October 2020 to March 2021. Aviadenoviruses (11.4%, 79/690) were predominantly detected, followed by siadenoviruses (6.2%, 43/690) and barthadenoviruses (1.3%, 9/690). Phylogenetic analysis demonstrated about half of the aviadenoviruses clustered with Duck adenovirus 2, revealing potential association with poultry animals. A high portion (67.2%, 88/131) of the DNA polymerase sequences had <85% identity to any known sequences, indicating the potential presence of novel species, particularly in bar-headed goose where adenoviruses of all three genera were detected for the first time. The clustering of adenovirus sequences from different birds and regions in the same branch of the phylogenetic analysis suggested their close genetic relationships, indicating the transmission of adenoviruses across bird species. Host exchange and recombination events were observed, which might reflect the plasticity of these viruses and the mechanism for the emergence of novel viruses. The prevalence and characteristics of the adenoviruses in migratory birds demonstrated the wide distribution of novel adenovirus species and possible transmission between wild birds and domestic animals.