Comparative pathogenicity of infectious bronchitis virus Massachusetts and Delmarva (DMV/1639) genotypes in laying hens

Muhammad Farooq; Reham M Abd-Elsalam; Natalya Ratcliff; Mohamed S H Hassan; Shahnas M Najimudeen; Susan C Cork; Sylvia Checkley; Yan Dong Niu; Mohamed Faizal Abdul-Careem

doi:10.3389/fvets.2023.1329430

Comparative pathogenicity of infectious bronchitis virus Massachusetts and Delmarva (DMV/1639) genotypes in laying hens

Front Vet Sci. 2024 Jan 19:10:1329430. doi: 10.3389/fvets.2023.1329430. eCollection 2023.

Authors

Affiliations

¹ Health Research Innovation Center, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada.
² Faculty of Veterinary Medicine, Cairo University, Giza, Egypt.
³ Department of Avian and Rabbit Medicine, Faculty of Veterinary Medicine, Assiut University, Assiut, Egypt.

Abstract

Infectious bronchitis (IB) is a highly contagious and acute viral disease of chicken caused by the infectious bronchitis virus (IBV) of the family Coronaviridae. Even with extensive vaccination against IB by the poultry industry, the occurrence of new IBV genotypes is a continuous challenge encountered by the global poultry industry. This experiment was designed to compare the pathogenicity of two IBV strains belonging to Massachusetts (Mass) and Delmarva DMV/1639 genotypes. Specific pathogen-free laying hens were challenged during the peak of production (30 weeks), keeping a mock-infected control group. During 21 days of observation following infection, a significant drop in egg production with miss-shaped and soft shells was observed in the DMV/1639 IBV-infected hens only. The DMV/1639 IBV infected group showed prolonged and higher cloacal viral shedding compared with the Mass IBV-infected group. At the end of the study (21 days post-infection), the viral genome loads in the respiratory, urogenital, and immune tissues were significantly higher in the DMV/1639 IBV-infected group compared with the Mass IBV-infected group. Macroscopic lesions such as distorted ova leading to egg peritonitis were observed only in the DMV/1639 IBV-infected group. Moreover, microscopic lesion scores were significantly higher in the lung, kidney, cecal tonsils, and oviduct of the DMV/1639 IBV-infected group compared with the Mass IBV-infected group. Finally, the apoptosis index in the kidney, ovary, magnum, isthmus, and shell gland was significantly higher in the DMV/1639 IBV-infected group compared with the control and Mass-infected groups. This study examined the pathogenicity of two IBV genotypes that are impacting the layer industry in North America.

Keywords: Delmarva (DMV)/1639 strain; Massachusetts (Mass) strain; apoptosis; infectious bronchitis virus; laying hen; pathogenesis.

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. We acknowledge funding from Agriculture and Agri Food Canada (AAFC) via Poultry Science Cluster funding to Canadian Poultry Research Council (CPRC, project number ASC-20) and Egg Farmers of Canada (EFC, grant number 10022788). PhD studies of MF is funded by the AHBP project of Higher Education Commission of Pakistan. The project was funded by joint funds from Canadian Research Council (CPRC) and Egg Farmers of Canada.