Epidemiological investigation and fiber gene genetic analysis of fowl adenovirus serotype 4 from 2017 to 2021 in Yunnan Province, China

Abstract

Abstract Background: In recent years, the prevalence of fowl adenovirus serotype 4 (FAdV-4) has caused huge economic losses to the Chinese poultry industry. The objective of this study was to determine the occurrence of FAdV-4 in Yunnan Province through an epidemiological investigation of poultry and wild birds from 2017 to 2021 and phylogenetic analysis of the isolated fiber genes. Results: The results showed that the FAdV-4 positive rate in poultry and migratory birds was 11.34% and 0.3%, respectively. The infection rate of the poultry tissue samples was high in central and west-ern Yunnan Province, and the infected hosts were mainly local chickens. Via the detection of common poultry infectious diseases prone to co-infection, it was found that the birds were mainly co-infected with pathogens such as infectious laryngotracheitis, chicken infectious anemia virus, and avian influenza virus. Five poultry-source strains and one wild bird-source strain were isolated, and phylogenetic analysis of these strains using the fiber gene showed that they all had high homology with the early Chinese highly pathogenic strains and clustered with the same genetic and evolutionary clade as the Chinese reference strain. The fiber protein is characterized by loci that indicate highly pathogenic strains (G219D, P307A, V319I, and A308T). Conclusions: The results of our study demonstrate that FAdV-4 continues to exhibit a high prevalence rate among poultry populations in Yunnan Province, China. Notably, we report the first detection of FAdV-4 in the feces of black-necked cranes. Our statistical analysis reveals that central Yunnan and western Yunnan experience a high incidence rate of FAdV-4, often accompanying co-infections with ILT, CIAV, and AIV.