Abstract The hydropericardium in chickens is most common in Isfahan and Chcharmahal-va-Bakhtiyari, Iran. For this, the study was achieved for investigation of adenovirus role in induction of hydropericardium in these regions. In this study, 20 broiler flocks suspected to hydropericardium were sampled from hydropericardi- um fluid. Then, DNA was extracted and amplified by specific primers. The amplified fragment for detection of AV was 896 bp. The results showed that 10 in 20 flocks, and 47 in 200 samples were positive to AV. The results revealed that most of infected flocks were more than 30 days old. In this study, the correlation between infec- tivity to adenovirus and husbandry system were not significant. The infectivity rate in Isfahan and Chaharmahal-va-Bakhtiyari was not significant. Therefore, in addition to high altitude, adenovirus infec- tion can play a role in increasing the prevalence of hydropericardi- um in these areas. Introduction Fowl Adenovirus (FAdV) belong to the genus of Aviadenovirus that have been associated to a number of disease conditions includ- ing Inclusion Body Hepatitis (IBH), Hydropericardium Hepatitis Syndrome (HPS), Gizzard Erosions (GE), proventriculitis and tenosynovitis. 1-3 This virus, like Mark’s disease virus, chicken ane- mia virus and Gamboro disease virus, can suppress the immune sys- tem. 4 The immunosuppression is a common property of most aden- oviruses infection in chickens that is manifested by lymphocytic depletion in bursa, thymus and spleen. 1 Adenoviruses are categorized into 4 genera: Mastadenovirus (in mammals), Aviadenovirus (in birds), Adenovirus (in birds, mam- mals and reptiles) and Siadenovirus (in birds and amphibians). 2 The International Committee for Taxonomy of Viruses (ICTV) proposed twelve serotypes for Aviadenovirus classification, based on serum neutralization test. Already, FAdV could be classified into five species, based on molecular structures, including A to E genotypes. 3 There exists a correlation between the FADV genotypes and serotypes. Genotype A includes FAdV1, type B: FAdV5, type C: FAdV4 and 10, type D: FAdV2, 3, 9 and 11 and genotype E contains FAdV6, 7, 8a and 8b. 1 Serotype 4 which is a member of the species FAdV C has been implicated in HPS. 2 HPS is caused by hydropericardium and hepatic necrosis. HPS was also known as Angara Disease: the first outbreak was observed in Pakistan in 1987, 1 and it was subsequently reported in many countries, including most middle east countries, resulting in signif- icant economic losses to poultry industry. 3 HPS is typically observed in 3 to 5 weeks of age in chickens and is characterized by mortality range from 30% to 70%. 2 The main lesions of HPS are hepatitis and hydropericardium. 5 Until now, HPS has been reported in many countries, including Iraq, Kuwait, India, Mexico, Ecuador, Peru, Chile, USA, Russia, Japan, and Poland, resulting in considerable economic losses. 3 The clinical and gross lesions of HPS in broilers in Iran has been showed but so far there is no scientific report relating to adenoviral HPS. So, PCR technique as a specific and rapid technique for detection of FAdV was utilized in this study for the identification of fowl aden- ovirus in HPS cases in broiler chickens. Correspondence: Ezatollah Fathi Hafshejani, Faculty of Veterinary Medicine, Shahrekord Branch, Islamic Azad University, Shahrekord, Iran. E-mail: Ezzatfathi@yahoo.com Key word: adenovirus; broiler chickens; hydropericardium. Acknowledgments: this research has been financially supported by Islamic Azad University, Shahrekord Branch, Shahrekord, Iran. Conflict of interest: the authors declare no conflict of interest. Availability of data and materials: all data generated or analyzed dur- ing this study are included in this published article. Ethics approval and consent to participate: the Ethics Committee of Veterinary Medicine Faculty of Islamic Azad University-Shahrekord Branch approved this study (IAU.Shk.971101). The study is con- formed with the Helsinki Declaration of 1964, as revised in 2013, concerning human and animal rights. Received: 1 April 2022. Accepted: 18 November 2022. Early view: 31 March 2023. Publisher’s note: all claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organi- zations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher. © Copyright: the Author(s), 2023 Licensee PAGEPress, Italy Journal of Biological Research 2023; 96:10353 doi:10.4081/jbr.2023.10353 This article is distributed under the terms of the Creative Commons Attribution-NonCommercial International License (CC BY-NC 4.0) which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited. [page 36] [Journal of Biological Research 2023; 96:10353] Journal of Biological Research 2023; volume 96:10353 The detection of fowl adenovirus in chickens with hydropericardium syndrome in Isfahan and Charmahal-Va-Bakhtiyari provinces, Iran Ezatollah Fathi Hafshejani, 1 Majid Gholami-Ahangaran, 1 Maryam Sami 2 1 Department of Poultry Diseases, Faculty of Veterinary Medicine, Shahrekord Branch, Islamic Azad University, Shahrekord; 2 Graduated of Veterinary Medicine Faculty, Shahrekord Branch, Islamic Azad University, Shahrekord, Iran Non-commercial use only