Immune response of chickens to various routes of administration of Australian infectious bronchitis vaccine.

Groups of 100 two-week-old cockerels were vaccinated with the A3 strain of IB vaccine by conjunctival, intranasal, in-contact, drinking water, or aerosol routes, or were left as unvaccinated controls. Three weeks after vaccination, each group of chickens was challenged with the Appin strain of IBV. Vaccination by the conjunctival, intranasal and in-contact routes induced a good resistance to challenge, concurring with an obvious stimulation of the Harderian gland, while the drinking water route led to a low resistance to challenge, with minor changes in the gland. The results of no immune response and no resistance to challenge in the birds vaccinated by aerosol route was due to unsuccessful vaccination in the group. Application of the vaccine by the conjunctival route would appear to be a most effective route for the application of Australian IB vaccines, while the in-contact method appears worthy of further study.