Impact of early infection by inclusion body hepatitis (IBH) virus on the efficacy of an infectious bronchitis (IB) live variant vaccine in commercial broiler chickens: a comprehensive study on clinical, histopathological, and virological parameters

Abstract

Adenoviruses are commonly found in chickens, and can be isolated from both sick and apparently healthy birds. Inclusion body hepatitis (IBH) is an acute disease primarily caused by (Fowl adeno virus) FAdV strains from groups D and E, including FAdV-8a serotype. Acknowledged for its immunosuppressive effects, we undertook an investigation into the early infection dynamics of IBH and its consequential impact on a fundamental vaccine widely employed in the poultry industry. Our study precisely examined the interplay between early IBH infection and the efficacy of a specific (Infectious bronchitis) IB vaccine. In this study, a total of 150 broiler chicks were divided into five groups, each consistedof 30 chicks. Group I received one dose of the IB variant vaccine, Group II and III received two doses (the first at 1-day-old and the second at 14-day-old), Group IV (control +ve) and Group V (control -ve). Groups I, II and IV were infected with IBH at 7-day-old. The evaluation encompassed diverse parameters, including clinical manifestations, mortality rates, and histopathological assessments of the liver, trachea, and kidney. Additionally, viral shedding of the IB vaccinal strain was examined. Our findings focus the detrimental impact of early IBH infection on avian organs and IB vaccinal strain shedding. Pronounced necrotic changes were observed in the tissues, coupled with an elevated viral shedding of the variant strain. These results collectively imply an augmented risk of potential outbreaks, emphasizing the need for a nuanced approach in managing IBH in the context of vaccination strategies.