Bulk milk investigation of Streptococcus agalactiae in Swedish dairy cattle herds
The aim of the study was to get an indication of how common Streptococcus agalactiae (SRA) is in large (>100 cows) free-stall dairy cow herds with conventional milking by investigating presence of SRA in bulk milk using PCR-technique. From almost all Swedish dairy cattle herd fulfilling the criteria one bulk milk sample per herd was taken using routine technique by the driver of the milk collector during the period April to June 2011. The samples were send to SVA for analysis using PCR (PathoProof™ Mastitis PCR Assay, Finnzyme).
In total, a likely infection with SRA was identified in 8.3% of the herds investigated which was somewhat higher than anticipated. This means that both farmers and veterinarians must be very observant to make sure that the infection is not introduced to a free herd and that an already introduced infection is detected as soon as possible to avoid spread within the herd. Important preventive measures are to avoid buying animals from other herds or only buy animals from herds which have been declared free from SRA. This can be controlled by repeated PCR-analyses of bulk milk samples over time.