Tehran University of Medical Sciences Iranian Journal of Microbiology 2008-3289 10 1 2018 02 26 65 71 EN Shima Shokri Department of Clinical Sciences, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran Vahid Karimi Department of Clinical Sciences, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran Arash Ghalyanchi Langeroudi Department of Microbiology and Immunology, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran Mehdi Vasfi Marandi Department of Clinical Sciences, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran Masoud Hashemzadeh Razi Vaccine and Serum Research Institute, Agricultural Research and Extension Organization, Tehran, Iran Taha Zabihipetroudi Department of Clinical Sciences, Faculty of Veterinary Medicine, University of Tehran, Tehran, Iran Hamideh Najafi Department of Pathobiology, School of Veterinary Medicine, Shiraz University, Shiraz, Iran Farshad Tehrani Department of Health and Management of Poultry Diseases, Iranian Veterinary Organization, Tehran, Iran 2016 11 25 Background and Objectives: Different epidemiological studies have found that backyard chickens are a reservoir for poultry diseases. Most backyard chicken flocks have a poor level of biosecurity, which increases the risk of spread of diseases. In recent years, the number of backyard chickens has been on the rise in Iran. However, the health status of backyard flocks is still poorly documented. Thus, this study aimed at examining the seroprevalence of antibodies against infectious bronchitis virus (IBV) and molecular surveillance and genotyping of IBV among backyard chickens (without vaccination history) in Mazandaran province, North of Iran, 2014. Materials and Methods: A total of 460 blood samples of unvaccinated backyard chickens in the mentioned area were tested for antibodies against IBV using commercial ELISA. Also, cecal tonsils were collected from 75 chickens in the same area. Real time RT-PCR (for detection) and RT-PCR and sequencing spike gene were performed. Results: The seropositivity rate was 54.5%. In addition, we detected 793/B, Variant 2, and QX in the backyard flocks and performed phylogenetic studies on them. The phylogenetic study revealed that the detected genotypes had high homology with IBV strains that were infected broilers, pullets, and layers in Iran. Conclusion: There is a need for continuous monitoring of IBV among avian species to complete the epidemiological map and work on the pathogenesis of Iranian IBV strains in Iranian backyard chickens. https://ijm.tums.ac.ir/index.php/ijm/article/view/1211 https://ijm.tums.ac.ir/index.php/ijm/article/download/1211/783