Paratuberculosis (Johne's disease) is a contagious and chronic infection caused by Mycobacterium avium subsp paratuberculosis that affects the small intestine of ruminants and other animals. In dairy cattle, Johne's disease can cause economic losses to dairy operations as a result of a reduction in milk production, lower slaughter value, and suboptimal culling.
Investigators have used various approaches and techniques in an attempt to quantify the economic losses of Johne's disease in dairy cattle.1,2 Estimates of losses vary widely as a result of differences in prevalence, herd and production performance, and study design, among other factors. Nonetheless, from the perspective of a producer deciding how to proceed with management and control of Johne's disease, knowing the losses caused by Johne's disease is insufficient information for making decisions. Producers also need an estimate of future losses that can be prevented by various control measures and how much those control measures will cost. Analysis based on these 3 components (estimated losses with and without control of the disease and costs of control programs) can be used to estimate return on investment, and an appropriate economic decision can be made.
Investigators have used various computer simulations in an attempt to estimate the costs and benefits of a range of control efforts for Johne's disease.3–5 Although simulation studies are widely used and provide a range of advantages (such as decreased cost and less time [ie, duration of the study]), compared with field studies, they can be difficult to validate. In addition, simulations require field data as an input (often complemented with expert opinion).
Investigators have examined losses attributable to Johne's disease6 and the costs and benefits for use of a vaccine.7 To our knowledge, no large-scale field trial has been conducted to evaluate the costs and benefits of management-related practices to control Johne's disease. A likely reason that so few studies have attempted to quantify both the costs and benefits is that to estimate reductions in losses, a study would need to be of sufficient duration to account for changes in herd performance related to control of Johne's disease. For example, in the case of management-related practices used to control Johne's disease, a minimum of 3 years is required because the intent of such practices is to limit infection of young calves, and clinical signs of Johne's disease do not often manifest before the cattle reach 3 years of age. In addition, field trials typically have considerably higher costs than do simulation studies or case-control studies.
The NJDDHP, which is a field trial, was started in 2003 and has been described elsewhere.a The main goal of the project is to evaluate the long-term feasibility and effectiveness of management-related practices designed to control Johne's disease on dairy cattle operations. The study reported here was performed to determine the farm-level economic costs and benefits for herds involved in the NJDDHP.
National Johne's Disease Demonstration Herd Project
Net present value
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