Effect of a herd specific vaccine against Staphylococcus aureus in a dairyherd

A controlled field experiment was performed in order to study the effect of a herd specific vaccine on prevalence of infections with Staphylococcus au reus (S.aureus), somatic cell count (SCC) and on the frequency of clinical mastitis in a dairy herd with a high prevalence of S.aureus. Animals of the herd were divided randomly among two groups: vaccination group (n = 35) an d control group (n = 36). Animals of the control group received a placebo i nstead of the vaccine. The vaccine or the placebo were administered subcuta neously in the area of the supramammary lymph nodes according to the follow ing protocol: all animals: basic immunization (twice three weeks apart); co ws: booster dose at the time of drying off, five and two weeks before calcu lated calving date; heifers: booster dose two and five weeks before calcula ted calving date. Udder quarter milk samples were collected monthly and sub jected to cytobacteriological examination. At this time, animals were also checked for signs of clinical mastitis. In order to compare the SCC in indi vidual whole milk samples, records hom the monthly milk quality testing wer e evaluated. Cow and udder quarter prevalence of S.aureus intramammary infe ctions did not differ between groups. However, during the lactation period following the booster dose, prevalence of Saureus increased in both groups (P < 0.05). There was no difference in prevalence of clinical mastitis due to S.aureus (cows and udder quarters) between vaccination and control group (P > 0.05). Clinical mastitis was more often caused by pathogens other tha n S.aureus (P < 0.05). Somatic cell count in whole milk samples did not dif fer between groups, but increased during lactation (P < 0.001). In summary, the herd specific vaccine tested in a dairy herd with a high prevalence of S.aureus did not proof to be efficacious in reducing the prevalence of S.a ureus infections or clinical mastitis due to S.aureus. Furthermore, there w as not influence on SCC in whole milk samples.