A field trial with an experimental vaccine against Staphylococcus aureus mastitis in cattle. 1. Clinical parameters.

A total of 108 heifers were included in a placebo-controlled multicenter study on the use of an experimental Staphylococcus aureus mastitis vaccine containing whole, inactivated bacteria with pseudocapsule, alpha and beta toxoids, and a mineral oil as adjuvant. The heifers were injected in the area of the supramammary lymph nodes twice before calving and were observed and sampled throughout the first lactation. None of the vaccinated cows suffered from clinical Staph. aureus mastitis, and only 8.6% suffered from subclinical Staph. aureus mastitis, but a total of 16.0% of the control cows suffered from clinical or subclinical Staph. aureus mastitis. Mean SCC in vaccinated and control cows were the same throughout the lactation. Local swellings at the injection site were palpable in a substantial proportion of the vaccinated cows. In the statistical analyses, when cow was used as the unit of concern, no significant differences occurred between groups. However, when all parameters on udder health were considered together, the results indicated a potential protective effect of this vaccine during the entire lactation.

A field trial with an experimental vaccine against Staphylococcus aureus mastitis in cattle. 2. Antibody response.

A Staphylococcus aureus vaccine containing whole, inactivated bacteria with pseudocapsule and alpha and beta toxoids with a mineral oil as adjuvant, was used in a field trial. Heifers were injected in the area of the supramammary lymph nodes with vaccine or placebo twice before calving and observed and sampled throughout their first lactation. Antibody response toward the pseudocapsule and the alpha toxin was significant in serum from the vaccinated cows. These antibody concentrations were significantly higher in serum and milk during the entire lactation compared with that of the controls. The antibody response to the beta toxin was moderate in serum from vaccinated cows; no differences in antibody concentrations in milk were significant between groups. The antibody response to the pseudocapsule consisted of the IgG1 and IgG2 isotypes, but, in milk, only the concentration of IgG1 was significantly increased in the vaccinated cows during the lactation compared with the control cows.