Characterization of Nephropathogenic Infectious Bronchitis Virus DMV/1639/11 Recovered from Delmarva Broiler Chickens in 2011

SUMMARY. A limited outbreak of nephropathogenic infectious bronchitis (NIB) occurred in three Delmarva (DMV) commercial broiler chicken flocks in 2011. Isolates of NIB virus (NIBV)—DMV/1639/11, DMV/3432/11, and DMV/3902/11—were characterized by sequence analysis of the N-terminal subunit (S1) of the spike (S) gene. Findings indicated that the isolates were identical to each other and to PA/9579A/10, a 2010 isolate from poultry in Pennsylvania. The 2010 and 2011 isolates appear to have originated from a 1997–2000 NIB outbreak in Pennsylvania. DMV/1639/11 and PA/9579A/10 were determined to be nephropathogenic in susceptible chickens, yielding virus reisolations from kidney and inducing characteristic interstitial nephritis microscopic lesions. In a controlled laboratory study, 40% of chickens vaccinated with a combination live vaccine containing infectious bronchitis virus (IBV) strains Massachusetts (Mass) + Connecticut (Conn) were positive on virus isolation attempts after challenge with DMV/1639/11, comp...