[Failure of anti-symptomatic vaccination and the methods of vaccine activity control].

Blackleg (Clostridium chauvoei) infection in Charollais cattle appears to have undergone some etiological and pathogenic changes which are reflected in the apparent failure of vaccination. Two methods have been used to determine the quality of the vaccines in order to meet the different requirements specified by pharmacopeias. The two methods differ in the vaccination schedules of the guinea pigs and the test strain used which may be either a virulent culture or a suspension of spore in calcium chloride. Both methods appear to be efficient in selecting vaccines which provide good protection. It follows, therefore, that the vaccination failures would appear to be the result of intensive selection of beef cattle with reduced immunological response. If this is the case, the remedy for these vaccination failures might lie in an adaptation of the vaccination schedule to the early developing breeds of cattle obtained by intensive selective breeding.