Effectiveness of simulated interventions in reducing the estimated prevalence of E. coli O157:H7 in lactating cows in dairy herds.

A transmission model developed to investigate the dynamics of Escherichia coli O157:H7 bacteria in a typical Dutch dairy herd was used to assess the effectiveness of vaccination, diet modification, probiotics (colicin) and hygienic measures as to water troughs and bedding, when they are applied single or in combination, in reducing the prevalence of infected animals. The aim was to rank interventions based on their effectiveness in reducing the baseline prevalence of infected animals in the lactating group. The baseline prevalence of the lactating group and the within-herd prevalence were estimated by the model to be 5.02% and 13.96% respectively. The results show that all four interventions, if applied to all four animal groups or only to young stock, are the most effective and will reduce the baseline prevalence by 84% to 99%. In general, combinations of hygiene (applied in all groups) and one other intervention had the highest effectiveness in reducing prevalence in the lactating group. Vaccination and diet modification show a slightly higher effectiveness than colicin and hygiene.