Effect of IBV D1466 on egg production and egg quality and the effect of heterologous priming to increase the efficacy of an inactivated IBV vaccine

Abstract

To protect layers, breeders and grandparents against damage by infectious bronchitis virus (IBV) infections during the laying period, vaccination using live priming followed by a boost with inactivated IB vaccine is commonly used. For many IB variants, homologous live vaccines are not available for priming. Very little is known about the efficacy of priming with heterologous live IB vaccines (or combination of live IB vaccines) to induce broad IB protection in long living chickens. In this study, the protection levels induced by vaccination programs with only a heterologous live priming by a Massachusetts and a 4/91 vaccine, only a multivalent inactivated vaccine that contained D1466 antigen and a combination of both, against a D1466 challenge were compared.The infection with IBV D1466, a genotype II, lineage 1 virus was able to cause serious damage to the unvaccinated laying hens resulting in respiratory signs, a long-lasting drop in egg production and loss of egg quality. All three vaccination programs induced significant levels of protection against challenge with a pathogenic D1466 strain. Overall, the vaccination program using the broad heterologous live priming and the inactivated vaccine provided high protection against the combination of egg drop and loss of egg quality. The results showed that the used combination of heterologous live vaccines was able to increase the efficacy of the inactivated IBV vaccine despite the very low antigenic relationship of both live vaccines with the challenge strain.