Some observations on the quality control testing of Clostridium chauvoei vaccines.

Agglutination tests are not suitable for the estimation of the protective antibody level in the sera of vaccinated animals and should not be used for the quality control testing of blackleg vaccines. Some highly virulent strains of Cl. chauvoei are only effectively protected against by vaccines containing cells with a heat labile protective antigen in addition to the heat stable antigen common to all cells of Cl. chauvoei. As these highly virulent strains may be encountered in the field it is important that such strains should be selected for the challenge of vaccinated animals in the quality control testing of blackleg vaccines. It would be useful if an international center could be responsible for the collection and distribution of such strains.