Direct and indirect effects of subclinical mastitis treatment in dairy herds

The objective of this research is to evaluate the impact of treatment of subclinical mastitis on duration of infection and mastitis transmission in dairy herds. We describe the use of a deterministic state-transition model of intramammary infections (IMI) to predict the impact of subclinical mastitis treatment programs in populations of lactating dairy cattle. Results of model simulations indicate that the parameters duration of infection and the transmission coefficients influence the steady state values for the proportion of cows infected. The theoretical model predicts that a reduction in the duration of subclinical infections caused by contagious pathogens leads to a decrease in the prevalence and incidence of new IMI among susceptible individuals. Thus the model demonstrates potential indirect effects of mastitis treatment interventions resulting from changes in the intensity of pathogen transmission within a herd.