Efficacy of a polyvalent mastitis vaccine against Staphylococcus aureus on a dairy Mediterranean buffalo farm: results of two clinical field trials

BACKGROUND: In the last years the knowledges on Mediterranean Buffalo (MB) mastitis is remarkably improving, nevertheless the attention has been never focused on vaccination as preventive strategy for the control of mastitis in these ruminates. The aim of the current study was to assess clinical efficacy over time of two different preventive vaccination protocols against S. aureus mastitis, in primiparous MB.Vaccinated (VG) and not-vaccinated (N-VG) groups, of 30 MB each one, were selected from two different herds (herd A: VG1 and N-VG1; herd B: VG2 and N-VG2) of the same farm. Herd A received a double vaccination (Startvac®, 45 and 10 days before calving, protocol A), while in herd B an additional administration was performed (52 days after calving, protocol B). Bacteriological milk culture and assessment of somatic cell count (SCC) were performed at 10, 30, 60 and 90 days in milk (DIM) from composite milk samples. After 90 DIM, daily milk yields and SCC values were monthly detected until dry-off. RESULTS: The overall incidence of positive MB for S. aureus was 40.8% (49/120) in VG1 and 43.3% (52/120) in N-VG1 (Protocol A), while 45.8% (55/120) and 50.8% (61/120) in VG2 and N-VG2 (Protocol B). The latter was associated with a significant decreased in prevalence (at 90 DIM) and incidence of mastitis (animals positive for S. aureus, SCC > 200^10³, with or without clinical signs) in the vaccinated MB, while no difference occurred in protocol A. Moreover, herd B showed a significant reduction in prevalence of intramammary infection (animals positive for S. aureus, SCC < 200^10³, no clinical signs) in the vaccinated MB at 60 DIM while no differences were detected in herd A, at any sampling time; N-VG2 had significantly higher overall SCC values than VG2 (4.97 ± 4.75 and 4.84 ± 4.60 Log10 cells/mL ± standard deviation, respectively), while no differences were recorded in herd A. CONCLUSIONS: The current investigation explores for the first time the clinical efficacy of vaccinations against S. aureus infections in MB, showing encouraging results regarding reduction in mastitis and somatic cell count; the polyvalent mastitis vaccine may be considered an additional tool for in-herd S aureus infection and should be associated to other control procedures to maximize its properties.