Managerial risk factors of intramammary infection with Streptococcus agalactiae in dairy herds in Ohio

Dairy herds in Ohio were selected by stratified random sampling for participation in a disease-monitoring study to relate Streptococcus agalactiae intramammary prevalence to herd management and environmental conditions. Of 48 herds studied, 27 herds had at least 1 cow infected with this pathogen. Management and environmental conditions were assessed by direct observation as well as by an interview with the dairy producers. One-way ANOVA or chi 2 analysis, with presence or absence of Streptococcus agalactiae as the dependent variable, was used to test each of 70 independent variables. Variables found significant at P less than 0.20 were further evaluated by use of logistic regression. Our sample size permitted only 4 independent variables to be simultaneously evaluated by logistic regression. The most predictive risk factors were identified as poor teat and udder hygiene, poor environmental sanitation, large herd population, and use of a shared washcloth for premilking cleaning of teats and udders.