Prevalence of Pathogens Causing Subclinical Mastitis in Argentinean Dairy Herds

The objective of this study was to investigate the prevalence of different mastitis pathogens in Argentinean dairy farms. Composite milk samples were collected of 2296 cows from 51 randomly selected herds in Córdoba, Argentina. Somatic cell count was determined in all samples and bacterial examination of the milk samples with a SCC exceeding 200,000 cells/mL was performed. Of all the cows, 54% were diagnosed with subclinical mastitis (SCC ≥200,000/mL). Bacteria were isolated in 83.1% of milk samples subjected to bacteriological analysis. The most frequently isolated pathogen was coagulase-negative staphylococci (CNS) (52.1%), followed by Staphylococcus aureus (21.3%), Corynebacterium spp. (5.2%), Streptococcus agalactiae (4.4%) and Streptococcus dysgalactiae (4.4%). This study demonstrates that among the major pathogens isolated, the contagious bacteria caused most of the subclinical infections of dairy cows in Cordoba, Argentina. Moreover, CNS was the most relevant group of minor pathogens causing subclinical mastitis.