EN
As a consequence of the negative evaluation of the effect of prophylactic vaccination against strangles (while using intramuscular injection of a bacterin or a vaccine containing the M protein of Streptococcus equi), appropriate research was started to achieve a progress in this area. It resulted in the isolation and characterization of the protective antigen, a polypeptide of mw about 41 000. Protective antibodies (IgA and IgG), specific for this antigen, were localized in the nasopharyngeal mucus of immune horses. These intibodies differed in specificity from bactericidal antibodies of the serum. The resistance against the disease appeared to be dependent on the nasopharyngeal antibodies and not the bactericidal serum antibodies. It was recommended to replace the intramuscular injections of the inactivated bacterin by intranasal application of an atomized suspension of a culture of an avirulent strain of Str. equi containing the polypeptide of mw 41 000.