Prevalence of Mastitis Pathogens in Herds Participating in a Mastitis Control Program

Open Access
Publisher Website
Google Scholar
Abstract
Bacteriological data from herd surveys by the Massachusetts [USA] Mastitis Laboratory were analyzed. Comparisons of percent cows and quarters with major mastitis pathogens and types of bacteria isolated were between Streptococcus agalactiae-positive (1105 cows from 17 herds) and S. agalactiae-negative herds (1088 cows from 17 herds). Major mastitis pathogens were isolated from 58.5% of cows and 37.0% quarters in S. agalactiae-positive herds. The most frequently isolated bacteria were S. agalactiae and Staphylococcus aureus, and together these accounted for 87% of organisms isolated. Major mastitis pathogens were isolated from only 26.3% of cows and 10.2% of quarters in S. agalactiae-negative herds. Streptococci other than S. agalactiae, S. aureus and coliforms were the predominant organisms isolated. Additional S. agalactiae-negative herds (17) were surveyed annually over 6 yr. An average of 25.8% cows and 10.3% quarters were positive for major mastitis pathogens during this time. The predominant bacteria isolated were streptococci other than S. agalactiae, S. aureus and coliforms. There was little variation between years.