Duration of immunity with Mycoplasma synoviae: Comparison of the live attenuated vaccine MS-H (Vaxsafe MS) with its wild-type parent strain, 86079/7NS

Abstract

The duration of protective immunity elicited by the MS-H vaccine was evaluated by experimental challenge of chickens at 15 and 40 wk after eyedrop vaccination. Immunity induced by the parent strain of the vaccine, 86079/7NS, was also investigated for comparison. A serological response to Mycoplasma synoviae was detected in 89% to 100% of MS-H vaccinates and 86079/7NS inoculates at 15, 27, 30, 35, and 40 wk after inoculation. A significantly lower incidence of air-sac lesions and lower air-sac lesion severity were observed in both the MS-H vaccinated and the 86079/7NS inoculated groups, as compared to the unvaccinated controls, after both challenge points. Tracheal mucosal thicknesses in MS-H..