LOCAL VACCINATION WITH KILLED STREPTOCOCCUS-UBERIS PROTECTS THE BOVINE MAMMARY-GLAND AGAINST EXPERIMENTAL INTRAMAMMARY CHALLENGE WITH THE HOMOLOGOUS STRAIN

The ability of killed Streptococcus uberis to induce protection agains t mastitis when administered either into the cistern of the dry mammar y gland (intramammary vaccination) without adjuvant or subcutaneously with adjuvant was investigated. Bacteria a ere never reisolated from v accinated quarters following challenge with the same strain during the subsequent lactation, and no inflammatory response was detected. In c ontrast, following subcutaneous vaccination, milk from challenged quar ters contained very small numbers of bacteria, but these quarters did exhibit clinical disease, whereas quarters on nonvaccinated control an imals produced discolored, clotted secretion with large numbers of bac teria and somatic cells and required antibiotic therapy by 60 h postch allenge. There was a significant increase in the levels of S. uberis-s pecific immunoglobulin G1 (IgG1), IgG2, and IgM in milk following intr amammary vaccination and in the levels of specific IgG1 and IgG2 in mi lk following subcutaneous vaccination. Levels of specific antibody in serum were also elevated following vaccination by either route. Howeve r, despite this, there was no increase in the opsonic activity of seru m or milk. Both peripheral blood lymphocytes and dry-period mammary gl and lymphocytes showed strong proliferative responses to S. uberis in vitro following subcutaneous vaccination, but only mammary gland lymph ocytes responded following intramammary vaccination. It was concluded that the protection seen in vaccinated quarters did not appear to be r elated to levels of specific antibody or neutrophil function and was p ossibly brought about by the inhibition of bacterial growth.