Progress 10/01/07 to 09/30/10
Outputs
OUTPUTS: A conceptual framework for an infectious disease control model for livestock was developed and empirically applied to evaluate the economic and epidemiological consequences of various control strategies for Johne's disease in dairy herds. Implementation as a discrete optimal control model measures the long-term feasibility and profitability of various Johne's disease control methods in dairy herds. These controls include testing and culling using either a fecal culture test and or an enzyme-linked immunosorbent assay (ELISA) test, and various improved cow and calf hygiene changes. The model is currently being utilized in a new project which looks at the potential of vaccination for Myobacterium avium subsp. paratuberculosis as an economic optimal control by itself or in addition to other controls for Johne's disease. Another dairy herd model was conceptualized and constructed to capture the costs associated with the cross-reactivity of Myobacterium avium subsp. paratuberculosis (MAP) vaccination with Tuberculosis (TB) by incorporating TB testing diagnostics for non-MAP-vaccinated and MAP-vaccinated dairy herds. This dairy herd model is applicable to any dairy production region given an estimate of the probability of a TB outbreak and is thus useful for policy makers in determining the net benefit of MAP vaccination within a known TB region and assessing the associated tradeoffs. Further development and implementation of this model was completed under a new funded research project. PARTICIPANTS: Tauer, L.W., PI; Grohn, Y.T., Co-PI; Schukken, Y.H., Co-PI; Cho, J., PhD Graduate Student; Dressler, J. PhD Graduate Student TARGET AUDIENCES: Scientists who conduct research on Myobacterium avium subsp. Paratuberculosis, and veterinarians who advise farmers on effective methods to control Johne's disease prevalent on dairy farms. Articles will be drafted to appear in dairy management magazines and publications presenting the empirical results. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Empirical results indicate that control of Johne's disease would significantly improve dairy producers' profitability in a Johne's infected herd, especially in herds with high infection rates. Results show that elimination of Johne's disease in a dairy herd requires a long-term plan with implementation of at least one of the control strategies. Any Johne's Disease control method yields a higher Net Present Value of the farm's net cash flow compared to no control. The empirical results can help dairy producers understand the economic benefits of controlling Johne's Disease and also aid in developing a comprehensive and effective Johne's Disease control program. Implementing either additional calf-hygiene management or test-and-cull using a fecal culture test can control the disease, but these are most effective when combined with each other in reducing the infection rate in Myobacterium avium subsp. paratuberculosis (MAP) infected herds. These results provide information to professionals who advise farmers concerning control of Johne's disease in their dairy herd. The second constructed dairy herd model was used to determine the net benefit of MAP vaccination within known tuberculosis (TB) regions by comparing the benefit of MAP vaccination to the costs associated with the cross-reactivity with TB test results. An application of this dairy herd model to Minnesota and Michigan, where TB outbreaks have occurred, indicates that the expected social cost of cross-reactivity is minor. The net benefit of MAP vaccination exceeded the costs of cross-reactivity when compared to non-MAP-vaccinated herds within each of Minnesota's and Michigan's TB accredited regions; however, the aggregate social cost for non-MAP-vaccinated dairy herds was less than MAP-vaccinated herds given that a TB outbreak occurred. Although our model was applied to parameters in only two regions, our results demonstrate that vaccination for MAP can be beneficial even within a TB-affected region when testing for TB may involve a sequence of tests. These finding have implications in policy decisions concerning the use of MAP vaccination in a TB infected region. The funding for this project permitted the initial development of models that were more fully developed in a project funded by USDA-CSREES award number 2008-35204-04627 and the Johne's Disease Integrated Program (JDIP, USDA) contract number 45105.
Publications
- Cho, J., Tauer, L., Smith, R., Lu, Z., Schukken, Y., and Grohn, Y. 2009. Economic Analysis of Johnes Disease Control Strategies for Dairy Herds. Poster presented at the 10th International Colloquium on Paratuberculosis, Minneapolis, Minnesota, USA, August 2009.
- Cho, J., Tauer, L.W., Schukken, Y.H., Smith, R.L., Lu, Z., Grohn, Y.T. 2010. Economic Analysis of Johnes Disease Control Strategies in Dairy Herds, Poster presented at the Agricultural and Applied Economics 2010 Meetings,Denver, Colorado
- Dressler, J., Smith, R., Tauer, L., Schukken, Y., and Grohn, Y. 2009. Costs Associated with Cross-Reactivity of Johnes Disease Vaccination with Tuberculosis in Dairy Cattle. Poster presented at the 10th International Colloquium on Paratuberculosis, Minneapolis, Minnesota, USA, August 2009.
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Progress 10/01/08 to 09/30/09
Outputs
OUTPUTS: We constructed a representative optimal control model of a dairy herd with equation components that incorporate the spread of Johne's disease within the herd along with production and economic equations and constraints. Various controls for Johne's disease were modeled and analyzed to determine the most cost effective control and the fastest control to eliminate the disease from the herd. We also conceptualized and constructed a separate dairy herd model to capture the externalities associated with the cross-reactivity of vaccination for John's disease within a tuberculosis accredited region given a tuberculosis outbreak. The tuberculosis test model was constructed with and without Johne's vaccination and was used to determine the net benefit of Johne's vaccination within a tuberculosis region by comparing the benefit of Johne's vaccination (ex ante costs) to the extra costs associated with the cross-reactivity with tuberculosis test results (ex post costs). Our models and results for both projects were presented to scientist and veterinarians at the 10th International Colloquium on Paratuberculosis in August of 2009. The two models and empirical results are now being reviewed for separate journal publication. After successful review the final results will be disseminated more widely to the dairy industry. PARTICIPANTS: Tauer,L.W., PI; Grohn,Y.T., Co-PI; Schukken,Y.H., Co-PI; Cho, Jaesung, PhD Graduate Student; Dressler, Jonathan, PhD Graduate Student. TARGET AUDIENCES: Scientists and veterinarians who attended the 10th International Colloquium on Paratuberculosis in August of 2009. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The existence of Johne's disease even at only a 10 percent infection rate was found to be costly, easily justifying actions to control and then eliminate the disease from the herd. However, control of Johne's disease within a dairy herd requires a long-term plan. The basic strategy of testing and culling identified infected animals requires up to 30 years of implementation to be successful. Testing and culling was found to be most cost effective with a much quicker disease elimination of 6 to 8 years when combined with the implementation of additional calf-hygiene management to reduce the infection rate in farms where the disease is present. It was found that the cross-reactivity cost of testing for tuberculosis with Johne's disease was so low that Johne's vaccination should not be discouraged even within an accredited tuberculosis region given the low probability of tuberculosis infection of individual herds within the region.
Publications
- No publications reported this period
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Progress 10/01/07 to 09/30/08
Outputs
OUTPUTS: Johne's diseases is contacted by young stock but the disease symtoms do not become evident until the animal matures. Older infected animals then infect young stock. The impact of controlling the disease is thus not manifested until years into the future, with disease control often taking years. A discrete optimal control model was constructed to model the movement of infected and non-infected animals through age cohorts and infectious states. The model optimizes the Net Present Value of the dairy enterprise into the extended future. This model has been quantified with milk yields, infection transmission rates, prices and costs, and successfully solved. Our next step is to empirically use the model to explore the net benefit of various Johne's disease control mechanisms, such as test and cull programs, calving hygiene and rearing practices, and vaccination. Results will provide information on the most cost effective strategy, and importantly, the pervasiveness of the disease over time of the various control mechanisms. The model is sufficiently flexible to analyze any size dairy and feeding/milking system. PARTICIPANTS: Loren W. Tauer, principal investigator, constructed and tested the initial version of the discrete optimal control model. Yrjo T. Grohn and Ynte H. Schukken, also principal investigators, provided expertise in model development. Jaesung Cho, PhD candidate, Applied Economics and Management, refined the discrete optimal control model and quantified the empirical coefficients of the model. Zhao Lu, Post Doctoral Candidate, Epidemiology, worked on developing a vaccination model for Johne's to be used in the control model. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
We have not yet generated empirical results that are presentable to dairy producers, veterinarians and other researchers and administrators.
Publications
- No publications reported this period
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