A Hybrid Modeling Approach to Assess the Efficacy of Control Measures on Paratuberculosis on U.S. Dairy Farms
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Paratuberculosis, also known as Johne's disease or JD, is a chronic contagious infection, caused by Mycobaterium avium paratuberculosis (MAP). This fatal disease is incurable and causes considerable economic losses to the industry. Each year, the U.S. dairy industry loses over 200 million dollars due to the infection. Using the cattle movement data of six California dairy farms and Johne's disease transmission data, a mathematical model was developed to determine control policies that can minimize the likelihood of outbreaks and the incidence and prevalence of the infection in dairy farms. In particular, we have implemented a hybrid modeling approach that combines the between-pen cattle movements with progression of the infection in each pen to study the effect of cattle movement patterns on the spread of disease. Using the basic reproduction number, the infection risk in cattle in each pen and the entire farm was calculated. It is shown that the overall infection risk is substantially reduced when the average residence time and the population size in high risk pens are minimized. Using numerical simulations, spread of epidemic waves in dairy farms and impacts of control measures are numerically explored. It is shown that a single control measure is insufficient to prevent outbreaks. Whereas a combination of control measures such as test and cull, and intensive pen cleaning may lead to a disease-free environment in the dairy farms.
Table of Contents
Introduction -- Analysis of the movement data -- Modeling movement and Johne's Disease -- Modeling analysis and parameter estimations -- Conclusions and discussions -- Appendix A. Extra figures and tables