In order to compare the short-term efficacies of the live attenuated Mycoplasma gallisepticum (MG)
vaccine strains ts-11 and 6/85, four groups of SPF chickens were vaccinated with each of the
vaccines using
eye drop and
aerosol inoculations, and were subsequently challenged with a wild-type MG strain. When administered by the recommended routes (
eye drop for ts-11 and fine
aerosol for 6/85), both
vaccines induced substantial and comparable levels of protection against airsacculitis and
tracheitis caused by wild-type MG. The long-term efficacies of the two
vaccines administered by the recommended route were also assessed. Serum antibody responses and colonization of the
vaccines in the upper respiratory system were monitored at different time points after vaccination, and protective efficacies of the
vaccines were evaluated at 36 weeks post vaccination as above. Systemic antibody response following ts-11
eye drop vaccination was initially strong but reduced gradually over time while, in contrast, that to 6/85 spray vaccination was initially weak but increased over time. Kinetics of the antibody response to the
vaccines appeared to be correlated with the number of birds harbouring each
vaccine in their upper respiratory system throughout the sampling timepoints. Regardless of the levels of serum
antibodies or number of birds harbouring the
vaccine, both
vaccines induced substantial and comparable levels of protection against airsacculitis and
tracheitis caused by wild-type MG. Therefore, kinetics of systemic antibody response and persistence in the upper respiratory system varies between
vaccine strains; however, the levels of protection may not, at least up to 36 weeks post vaccination. RESEARCH HIGHLIGHTS The kinetics of systemic antibody response and persistence of the
vaccine in the upper respiratory system varies between
vaccine strains ts-11 and 6/85. The levels of protection induced by the two
vaccines against virulent MG strain challenge are comparable when they are administered by the route recommended by their manufacturers.