Tropism and infectivity of duck adenovirus type-3 virus in chickens

Abstract

Background Duck adenovirus type-3 (DAdV-3) seriously affects the health of ducks, however, the pathogenicity of the virus in chickens remains unknown. The objectives of the study were to evaluate the pathogenicity and major pathological changes caused by DAdV-3 in chickens. Results The specific fragment of the virus was amplified by polymerase chain reaction (PCR), and the evolutionary tree showed that the isolated virus belonged to DAdV-3, named HE-AN-2022. The mortality rate of chicks was 100% after subcutaneous inoculation at the neck, while the mortality rate of eye-nose drop inoculation was correlated with the number of infections, with 26.7% of chicks dying if exposed to multiple infections. The main symptoms of chicks before death were hepatitis-hydropericardium syndrome (HHS), ulceration of the glandular stomach and swollen bursa with petechial hemorrhages. Histopathological examination showed swelling, necrosis, lymphocyte infiltration and alkaline inclusion bodies in multiple organs. The results of quantitative real-time PCR (qPCR) showed that DAdV-3 could infect most organs of chickens, and the gizzard, glandular stomach, bursa, spleen and liver carried the highest amount of virus. Surviving chicks produced extremely high antibody levels. After infecting chickens with DAdV-3 derived from Muscovy ducks, no amino acid mutation was observed in the major mutation regions ORF19B, ORF66 and ORF67 of the virus. Conclusion DAdV-3 can infect chickens, causing classic HHS with ulceration of the glandular stomach and swollenbursa with petechial hemorrhages, leading to high mortality in chickens.The major variation domains did not change after infection with the virus in Muscovy ducks and chickens. This is the first study to report the of DAdV-3 in chickens, and this study provides a new basis for the prevention and control of the virus.