ROLE OF VACCINATION FOR PREVENTING STAPHYLOCOCCUS AUREUS AND COAGULASE-NEGATIVE STAPHYLOCOCCI INTRAMAMMARY INFECTIONS IN DAIRY HERDS.

The aim of this paper was to evaluate vaccine efficacy under field conditions against Staphylococcus aureus and Coagulase Negative Staphylococci (CNS) intramammary infections (IMI) in dairy cows. During the 21-month duration of the study, 1,156 lactations in 809 cows were identified in two herds. At the beginning of the trial, all cows that were due to calve were vaccinated until approximately 50% of cows in the milking herd were vaccinated (~6 months). At that point in time (50% vaccination coverage was reached), cows were systemically random assigned to be vaccinated or left as negative controls. Cows that were vaccinated got the 1st injection 45 days (+ 3 days) before the expected parturition date, the 2nd injection 35 days (5 weeks) thereafter (+ 3 days), corresponding to 10 days before the expected parturition date and 3rd vaccination was done at 52 days (+ 3 days) after the actual parturition date. Cure rate, risk of new infections, prevalence, incidence and duration of infections were analyzed. The farms showed a large difference in management to control infection during the study. In conclusion vaccination reduced the basic reproduction ratio of Staph. aureus by approximately 45% and for CNS by approximately 35%. Vaccination is a valuable tool in improving the incidence and prevalence of staphylococcal infection in herds. Vaccine utilization will need to be combined with excellent milking procedures, culling of known infected cattle and other management procedures to further reduce incidence and duration of infection.