Infectious bronchitis virus infection in laying hens

The effects of two Australian strains of infectious bronchitis virus (IBV-T and N1/88) were studied in unvaccinated Isa Brown laying hens (n=150). At 30 weeks of age, hens were divided into three groups and exposed to one of two strains of IBV, T strain or N1/88-strain, and one group was left unchallenged as a control. Both strains of IBV multiplied in the Harderian gland, trachea and simultaneously in the kidney and oviduct. The ultrastructural findings revealed that both strains were able to replicate in the albumen-forming regions of the oviduct. Both strains were responsible for deterioration in egg internal quality. There was no drop in egg production and deterioration of egg shell quality was only in terms of loss of egg shell colour and lower shape index. Both strains of IBV were isolated from the kidney, trachea, lower gut contents and faeces of infected laying hens. The virus was detected or isolated from the oviduct of infected hens from both challenge groups by RT-PCR and by chicken embryo inoculation. Both these diagnostic tests were found to be equally sensitive.