Decision analysis model for paratuberculosis control in commercial dairy herds

A previous economic test-and-cull decision analysis model has been strengthened and updated with current epidemiologic information. Created using Excel® and PrecisionTree® software, the model incorporates costs and benefits of herd management changes, diagnostic testing, and different management actions based on test results to control paratuberculosis in commercial dairy herds. This novel “JD-Tree” model includes a herd management decision node (four options), a test/no test decision node (two options), a diagnostic test choice decision node (five options), test result chance nodes (four levels of possible results), and test action decision nodes (three options; cull, manage, no action). The model culminates in a chance node for true infection status. Outcomes are measured as a net cost–benefit value to the producer. The model demonstrates that improving herd management practices to control infection spread (hygiene) is often more cost-effective than testing; not all herds should test as part of a paratuberculosis control program. For many herds, low-cost tests are more useful than more sensitive, higher cost tests. The model also indicates that test-positive cows in early stages of infection may be retained in the herd to generate farm income, provided they are managed properly to limit infection transmission. JD-Tree is a useful instructional tool, helping veterinarians understand the complex interactions affecting the economics of paratuberculosis control and to define the accuracy and cost specifications of better diagnostic tests.