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Abstract Background Fowl adenovirus is of major concern to the poultry industry worldwidely. In order to monitor the prevalent status of Fowl adenovirus in China, a total of 1920 clinical samples from apparently healthy birds in the 25 sites of poultry flocks, Slaughterhouse and living bird markets from 8 provinces in eastern China were collected and detected by PCR, sequencing, and phylogenetic analysis. Results The epidemiological survey showed that Fowl adenoviruses were detected in living bird markets, and circulating in a variety of fowl species, including chickens, ducks, goose and pigeons. Among the 1920 clinical samples, 166 samples (8.65%) were positive in the fowl adenovirus PCR detection. In this study, totally all the 12 serotypes (serotypes of 1, 2, 3, 4, 5, 6, 7, 8A, 8B, 9, 10 and 11) fowl adenoviruses were detected, the most prevalent serotype was serotype 1. Phylogenetic analysis indicated that 166 FAdVs of 12 serotypes were divided into 5 fowl adenovirus species (Fowl aviadenovirus A, B, C, D, E). Conclusions In the epidemiological survey, 8.65% of the clinical samples from apparently healthy birds were positive in the fowl adenovirus PCR detection. Totally all the 12 serotypes fowl adenoviruses were detected in a variety of fowl species, which provided abundant resources for the research of fowl adenoviruses in China. The newly prevalent FAdV serotypes provides valuable information for the development of an effective control strategy for FAdV infections in fowls.

Infection with fowl adenoviruses (FAdVs) can result in a number of syndromes in the production of chicken, including inclusion body hepatitis (IBH), hepatitis-hydropericardium syndrome (HHS), and others, causing enormous economic losses around the globe. FAdVs are divided into 12 serotypes and five species (A–E; 1–8a and 8b−11). Most avian species are prone to infection due to the widespread distribution of FAdV strains. The genus aviadenovirus, which is a member of the adenoviridae family, is responsible for both IBH and HHS. The most popular types of transmission are mechanical, vertical, and horizontal. Hepatitis with basophilic intranuclear inclusion bodies distinguishes IBH, but the buildup of translucent or straw-colored fluid in the pericardial sac distinguishes HHS. IBH and HHS require a confirmatory diagnosis because their clinical symptoms and postmortem abnormalities are not unique to those conditions. Under a microscope, the presence of particular lesions and inclusion bodies may provide clues. Traditional virus isolation in avian tissue culture is more delicate than in avian embryonated eggs. Additionally, aviadenovirus may now be quickly and precisely detected using molecular diagnostic tools. Preventive techniques should rely on efficient biosecurity controls and immunize breeders prior to production in order to protect progeny. This current review gives a general overview of the current local and global scenario of IBH, and HHS brought on by FAdVs and covers both their issues and preventative vaccination methods.

Introduction: Fowl adenoviruses (FAdV) cause inclusion body hepatitis (IBH) in chickens and new vaccination strategies against IBH are needed as an effective control measure in the poultry industry. Methods: The attenuated FAdV isolates from from chicken embryonated (UPM1137E20) and cell culture (UPM1137CEL35) were evaluated and compared based on sequence analysis of hexon and fiber genes. Their pathogenicities and immunogenicities were then determined in the commercial broiler chickens. Groups of chicken were inoculated with 0.5ml chicken-embryonated-derived attenuated FAdV isolates via oral and IP routes and sera, trachea, liver and gizzard samples were collected at days 3, 7, 14 and 21post-inoculation. Results: Molecular analysis revealed both isolates had 99.1% and 97.3% homologies in the L1 loop region of hexon gene and knob region of fiber gene, respectively. Molecular changes in UPM1137E20 were prominent in the knob of fiber gens with 3 amino acid changes, while for UPM1137CEL35, notable in the L1 loop region with 3 amino acid changes. It was demonstrated that both attenuated isolates are non-pathogenic and safe in commercial broiler chickens. Neither gross nor histopathological lesions were recorded in all tested groups. Both isolates induced high antibody response significantly via intraperitoneal route when compared to the control. Conclusion: UPM1137E20 isolate had a high potential to be further evaluated as a live attenuated vaccine against viral poultry diseases such as IBH.

Background: Fowl adenovirus serotype 4 (FAdV-4), causing inclusion body hepatitis (IBH) and hydropericardium hepatitis syndrome (HPS), is responsible for the significant economic losses in poultry industry worldwide. This study describes FAdV disease and molecular characteristics of the virus as the first report in UAE. Methodology: Clinical, necropsy, histopathology, qPCR and phylogenetic analysis of hexon gene were used to diagnose and characterize the virus. Results: The age of the infected broiler chicken was 2–4 weeks. The morbidity and mortality rates ranged between 50 and 100% and 44 and 100%, respectively. Clinically, sudden onset, diarrhea, anemia and general weakness were recorded. At necropsy, acute necrotic hepatitis, with swollen, yellowish discoloration, enlarged and friable liver; hydropericarditis with hydropericardium effusions; and enlarged mottled spleen were observed. Histopathology examination revealed degeneration and necrosis, lymphocytic infiltration and inclusion bodies. The qPCR analysis detected the virus in all samples tested. Hexon gene sequence analysis identified FAdV serotype 4, species C as the major cause of FAdV infections in UAE in 2020, and this strain was closely related to FAdV-4 circulating in Saudi Arabia, Pakistan, Nepal and China. Conclusion: The serotype 4, species C, was the common FAdV strain causing IBH and HPS episodes in the region. This result may help design effective vaccination programs that rely on field serotypes.