Contagious bovine pleuropneumonia-protection following natural infection and vaccination.

Cattle that recover from contagious bovine pleuropneumonia, the disease caused by Mycoplasma mycoides var. mycoides, are usually immune to reinfection. Prohylactic inoculation against the disease has been practiced for over a century and utilizes the fact that even virulent strains of M. mycoides inoculated subcutaneously into fully susceptible cattle only very rarely produce pneumonia, but instead produce subcutaneous lesions which may or may not kill the animals depending on various factors including the site of the inoculation and virulence of the strains. Animals that survive are immune to further local infections or to the natural disease. The most successful vaccines at present consist of live attenuated strains of M. mycoides which produce a slight local reaction at the site of inoculation. It appears that vaccines made from inactivated organisms are poorly immunogenic and may even sensitize the animals thereby causing them to react more severely to subsequent challenge.