Live Attenuated Infectious Bronchitis Virus Vaccines in Poultry: Modifying Local Viral Populations Dynamics

Infectious bronchitis virus (IBV) remains one of the most important diseases impacting poultry today. Its high adaptive capacity, attributable to the high mutation rate associated with its ssRNA(+), is one of its more important features. While biosecurity procedures and barriers have been shown to be preponderant factors in minimizing the impact of infectious bronchitis (IB), the environment and procedures associated with intensive poultry systems greatly influence the viral population dynamics. High-density poultry flocks facilitate recombination between different viruses, and even with live attenuated vaccines, which can change the dominant circulating field strains. Furthermore, the remaining issue of reversion to virulence gives rise to significant problems when vaccinal strains are introduced in places where their pathogenic variants have not been reported. Under specific conditions, live attenuated vaccines could also change the frequency of circulating viruses and enable replacement between different field strains. In summary, under a comprehensive approach, while vaccination is one of the most essential tools for controlling IB, the veterinarians, farmers, and official services role in its usage is central to minimizing alteration in a malleable viral population. Otherwise, vaccination is ultimately counterproductive.