Pathogenicity of Duck Adenovirus Type 3 in Chickens.

Simple Summary: This study aimed to evaluate the pathogenicity of duck adenovirus Type 3 (DAdV-3) in chickens. In this study, this virus was identified through the amplification of specific viral fragments and whole-genome sequencing, and its pathogenicity was identified by means of its inoculation into chickens. The isolated DAdV-3 led to higher pathogenicity and fatality rates in chickens. The main clinical symptoms in the sacrificed chicks were hepatitis–hydropericardium syndrome (HHS), swollen and petechial hemorrhages of the bursa, and the gizzard's endothelium falling off easily. Histopathological examination showed swelling, necrosis, lymphocyte infiltration, and basophilic inclusion bodies in multiple organs. Higher antibody levels were found in the surviving chickens. The major variation domains (ORF19B, ORF66, and ORF67) did not change after infection with the virus in Muscovy ducks and chickens. This is the first study to report the pathogenicity of DAdV-3 in chickens, and it provides an experimental basis for newly infected hosts of DAdV-3. Duck adenovirus Type 3 (DAdV-3) severely affects the health of ducks; however, its pathogenicity in chickens remains unknown. The objectives of this study were to evaluate the pathogenicity and major pathological changes caused by DAdV-3 in chickens. Viral DNA was extracted from the liver of the Muscovy duck, and the fiber-2 and hexon fragments of DAdV-3 were amplified through polymerase chain reaction (PCR). The evolutionary tree revealed that the isolated virus belonged to DAdV-3, and it was named HE-AN-2022. The mortality rate of chicks that received inoculation with DAdV-3 subcutaneously via the neck was 100%, while the mortality rate for eye–nose drop inoculation was correlated with the numbers of infection, with 26.7% of chicks dying as a result of exposure to multiple infections. The main symptoms exhibited prior to death were hepatitis–hydropericardium syndrome (HHS), ulceration of the glandular stomach, and a swollen bursa with petechial hemorrhages. A histopathological examination revealed swelling, necrosis, lymphocyte infiltration, and basophilic inclusion bodies in multiple organs. Meanwhile, the results of quantitative real-time PCR (qPCR) demonstrated that DAdV-3 could affect most of the organs in chickens, with the gizzard, glandular stomach, bursa, spleen, and liver being the most susceptible to infection. The surviving chicks had extremely high antibody levels. After the chickens were infected with DAdV-3 derived from Muscovy ducks, no amino acid mutation was observed in the major mutation regions of the virus, which were ORF19B, ORF66, and ORF67. On the basis of our findings, we concluded that DAdV-3 infection is possible in chickens, and that it causes classic HHS with ulceration of the glandular stomach and a swollen bursa with petechial hemorrhages, leading to high mortality in chickens. The major variation domains did not change in Muscovy ducks or in chickens after infection. This is the first study to report DAdV-3 in chickens, providing a new basis for preventing and controlling this virus. [ABSTRACT FROM AUTHOR]