SUMMARY An isolate of infectious bronchitis virus (IBV) from a commercial White Leghorn laying flock in Florida was found to be serologically different from Massachusetts, Connecticut, Gray, Holte, Iowa 97, Iowa 609, and JMK types. Two different Massachusettstype IB vaccine virus strains and Connecticut-type IBV failed to protect chickens against respiratory signs and infection in laboratory trials. In reciprocal cross-immunity tests when used as a vaccine the Florida isolate failed to protect satisfactorily against Massachusetts, Iowa 609, Iowa 97, Gray, JMK, and SE17 viruses. Good protection was obtained against Holte-type virus, a nephritis-inciting isolate, even though it was not related to it serologically. The virus was labile in the presence of chloroform, heat (56 C), and an acid pH (3.0). The affected flock from which the virus was isolated experienced a drop in egg production with a concurrent reduction in shell quality, though it had been vaccinated with Massachusetts and Connecticut IBV serotypes. The implication of the multiplicity of IBV serotypes and their impact on vaccination programs are discussed. It is suggested that the new isolate be designated Florida-type IBV.
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