Evaluation of Infectious Bronchitis Virus Arkansas-Type Vaccine Failure in Commercial Broilers

Infectious bronchitis virus (IBV) causes an upper respiratory tract disease in chickens and is highly contagious. Many different types of the virus exist, but only a few types are used as attenuated live vaccines in the commercial poultry industry. Of the vaccine types used, the Arkansas (Ark)–type virus is most frequently reisolated from vaccinated broilers. Previous research has suggested that incomplete clearance of Ark-type vaccine virus...