Emerging lethal infectious bronchitis coronavirus variants with multiorgan tropism

Area of Science:

• Veterinary Virology
• Poultry Disease Research
• Molecular Epidemiology

Background:

• Infectious bronchitis virus (IBV) is a significant cause of respiratory illness in chickens, impacting the global poultry industry.
• Despite vaccination programs, field outbreaks of IBV persist, particularly in Taiwan, indicating the emergence of new viral strains.
• Understanding these evolving IBV strains is crucial for developing effective disease management strategies.

Purpose of the Study:

• To characterize the genetic makeup, serotypes, and pathogenicity of emerging IBV variants circulating in Taiwan.
• To assess the effectiveness of existing commercial vaccines against these novel IBV strains.
• To identify potential recombination events contributing to the evolution of IBV in the region.

Main Methods:

• Analysis of structural protein genes to identify genetic variations and recombination events.
• Cross-neutralization tests to determine serological relationships between IBV variants and existing serotypes.
• Clinicopathological assessments in specific-pathogen-free (SPF) chicks to evaluate pathogenicity and organ tropism.

Main Results:

• Emerging IBV variants in Taiwan resulted from frequent recombination among local, Chinese, Japanese, and vaccine strains.
• Two novel serotypes were identified among the circulating IBV variants.
• The variants demonstrated high fatality rates (up to 67%) and multiorgan tropism in young chicks.
• A commercial live-attenuated Mass-type vaccine provided inadequate protection against these emerging variants.

Conclusions:

• Novel genotypes, serotypes, and pathotypes of IBV are circulating in Taiwan.
• These emerging variants pose a significant threat due to their pathogenicity and ability to evade existing vaccine-induced immunity.
• Urgent development of effective countermeasures, including updated vaccines, is required to control these IBV strains in the poultry industry.