Protection against airsacculitis with sequential systemic and local immunization of chickens using killed Mycoplasma gallisepticum bacterin with iota carrageenan adjuvant.

The induction of protective immunity to Mycoplasma gallisepticum (MG) by bacterins containing 0.2% iota carrageenan (iCGN) as an adjuvant has been studied. Various combinations of intracoelomic (i.c.), intratracheal (i.t.), intranasal (i.n.), intravenous (i.v.), subcutaneous (s.c.) and oral immunization routes were evaluated. Vaccinated and non-vaccinated groups were compared with a group vaccinated s.c. with a commercial bacterin. Primary i.c. immunization with the bacterin was as effective as commercial bacterin and was more effective when followed by i.n. or i.t. immunization. Oral immunization was ineffective, in contrast to observations reported with mice. The i.c./i.n. and i.c./i.t. combinations were the most effective, produced the highest levels of anti-MG IgG and IgA in serum and tracheobronchial washes, and sometimes provided 100% protection against air sac lesions. Chickens vaccinated by the i.c./i.n. or i.c./i.t. routes had the fewest virulent organisms in their respiratory tract secretions. These results demonstrated that i.c. immunization followed by local immunization with the bacterin is most efficacious in protecting chickens against airsacculitis.