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Determination of the protective efficacy of two vaccination strategies against infectious bronchitis (IB) in laying hens

2022 CPRF
An in vivo animal experiment was conducted in specific pathogen-free (SPF) female chickens to evaluate the protective efficacy of two immunization regimes against Massachusetts (Mass) serotype of infectious bronchitis virus (IBV) isolated from a layer flock with egg production problems in Alberta. The first immunization regime consisted only of consecutive doses of monovalent and bivalent live attenuated IB vaccines, while the second regime included both live attenuated and inactivated IB vaccines. To assess the protection, the hens were challenged with a standard dose of Mass type IBV isolate at the peak of lay. The protective efficacy of the two vaccination strategies were evaluated through the following parameters: (1) scoring of clinical signs, (2) egg production defects, (3) gross and histologic changes, (4) post-challenge serological response, (5) quantification of viral RNA in swabs at different time points and tissues, (6) detection of virus infected cells by immune staining techniques. Neither drop in egg production nor gross lesions could be observed in all hens. The birds in the two vaccination strategies exhibited no clinical signs in comparison with the non-vaccinated challenged birds. The other findings showed that the second vaccination strategy revealed minimal histological lesions in the reproductive tissues, no egg quality defects, as well as lower viral genome loads in the swabs at certain time points in comparison with the first vaccination strategy. In conclusion, the combination of live attenuated and inactivated vaccines in immunization schedule of layers could induce better protection against IBV challenge.
Tags :
infectious bronchitis,layers,vaccination
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PhD Student

University of Calgary

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