An experimental vaccine composed of two adjuvants gives protection against Mycoplasma bovis in calves

Mycoplasma bovis is a major pathogen affecting cattle causing bronchopneumonia, mastitis, and other disorders. Only autogenous vaccines made specifically for individual farms are available in parts of Europe and the United States. A novel experimental vaccine composed of a field M. bovis isolate combined with saponin and Emulsigen® adjuvants was evaluated. Eighteen 3-4 week old calves were placed in three equal groups: vaccinated (Vac), positive control (PC) and negative control (NC). The Vac calves were subcutaneously injected with 8 ml of the vaccine; the PC and NC calves received phosphate buffered saline (PBS). Three weeks later the Vac and PC calves were challenged with a virulent M. bovis strain, the NC group received PBS. Throughout the study clinical observations, microbiology and immunological tests were carried out. Three weeks post challenge two calves from each group were euthanased for necropsy and histopathological examination. The vaccine effectively stimulated the humoral immune response, with high titres of anti-M. bovis specific antibodies and total Ig concentration. This vaccine also intensified the IgA response. A clinically protective effect of the vaccine was demonstrated as it also reduced the gross pathological lung lesions and nasal shedding of M. bovis.