Infectious Bronchitis Virus Surveillance in Ontario Commercial Layer Flocks

SUMMARY Infectious bronchitis (IB) is one of the most important viral diseases of poultry and causes major economic losses to the industry. IB status in commercial layers in southern Ontario was assessed through a questionnaire. According to the data gathered from egg producers of Ontario, repeated outbreaks of IB occurred even though flocks had been routinely vaccinated. Based on this information, 13 farms throughout the region were selected for IB virus (IBV) surveillance. IBV vaccinated and unvaccinated sentinel birds were placed in barns with different IB histories, and after a 1-wk exposure tissues and pharyngeal swabs were collected and tested for the presence of IBV. An initial study indicated that tracheal tissues were more often positive than samples from cecal tonsils, kidneys, lungs, and pharyngeal swabs. Therefore, all subsequent IBV detection was directly on tracheal tissues with nucleocapsid (N) gene specific reverse transcription (RT) polymerase chain reaction (PCR). From the sentinel bird placements and N-gene RT-PCR analysis, IBV was detected on 11 farms with differing IB histories. The study indicated that farms with previous IB outbreaks could harbor the virus without clinical signs in the flocks. In addition, some farms, although they did not report having IB associated problems, were IBV positive by N-gene RT-PCR.