Safety and efficacy of the Mycoplasma synoviae MS-H vaccine in turkeys.

The live, attenuated, temperature-sensitive Mycoplasma synoviae (MS) vaccine strain MS-H is used to control virulent MS infection in commercial chicken flocks. However, the safety of this vaccine and its potential to prevent disease in turkeys have not been investigated. In this study, MS-H was shown to colonize the upper respiratory system and to induce an antibody response in turkeys but, even at the maximum release dose, was not found to cause air sac, joint, or tracheal lesions typical of wild-type MS infection. Histopathologic examinations of the vaccinated turkeys after exposure to a virulent MS challenge revealed that administration of the vaccine by aerosol, but not eye drop, at the dose recommended for chickens protected the birds against microscopic lesions and colonization of the virulent MS in trachea. It is concluded that MS-H vaccine is safe for use in turkeys and, when used as aerosol at the dose recommended for commercial chickens, can protect turkeys against tracheal lesions caused by a wild-type MS strain.