Experimental vaccination against Mycoplasma agalactiae using different inactivated vaccines.
Five sets of vaccines were prepared using Mycoplasma agalactiae washed cultures inactivated with phenol (1), formalin (2), heat-treatment (3), sodium hypochlorite (4) and saponin (5). All sets, except for saponin-vaccine, were adjuvanted with aluminium hydroxide. Five groups of six Sarda ewes were inoculated twice before pregnancy, once during pregnancy and challenged during the lactation period. Monthly blood samples were taken from the vaccinated sheep and from 12 controls: sera were assayed by immunoblotting, ELISA and growth inhibition tests. Four control sheep were infected by intra-canalicular route with pooled mycoplasmas at concentrations of 104, 105, 106 and 107 CCU. The challenge involved using infected milk to contaminate the remaining sheep. All the controls and some ewes from groups 2, 3 and 4 developed contagious agalactia. Ewes vaccinated with phenol- and saponin-inactivated mycoplasmas resisted experimental challenge. It is concluded that these two vaccines are effective and that their use could limit the diffusion of M. agalactiae infection.