| five-year longitudinal study was performed to better understand Johne's disease (JD) control in dairy cattle in terms of its impact on the environmental reservoir for the disease, the disease burden within the herd, and the cost-effectiveness of control programs. The objectives of this study were to: (1) describe the distribution Mycobacterium avium paratuberculosis (MAP) in the environment of infected dairy farms over time, and observe how that distribution changes as herd prevalence changes; (2) evaluate the effectiveness of management practices in reducing the JD burden within the herd; and (3) determine if the management practices implemented to control JD were cost-effective.;Seven dairy herds infected with JD participated in this study. Upon study enrollment, each herd implemented a JD control program designed specifically for that farm, based on a JD risk assessment and the operation's goals and capabilities. The risk assessment was repeated annually, and the control program modified as necessary. Within herd JD prevalence was monitored annually by fecal culture and/or serum ELISA testing of all adult cows. Every six months, samples of feed, water, and bedding were collected and cultured for MAP, from the pre-weaned calf, weaned calf, lactating cow, and maternity areas, as well as the primary manure storage area and pasture when appropriate. A questionnaire was developed and administered to each producer and/or herd manager yearly, to collect information on the costs incurred as a direct result of the JD control program. Based on the data collected, descriptive statistics were generated. Logistic regression was used to assess the effectiveness of management changes in preventing infection with MAP, and the net present value (NPV) of the each farm's JD control program was calculated.;Environmental contamination with MAP was consistent over time. When herd prevalence was >2%, MAP was cultured from the lactating cow floor and/or manure storage 75% of the time. When herd prevalence was <2%, MAP was never cultured from any area sampled.;Management practices associated with neonatal calf care were found to have the greatest impact on cows subsequently testing positive for JD as adults. Specifically, those factors were: exposure to adult cows other than dam at birth (OR = 1.09, 95% CI: 1.06--1.13), and feeding colostrum from one cow to multiple calves (OR = 1.10, 95% CI: 1.09--1.12). When designing JD control programs, implementing management practices that minimize the exposure of newborn calves to Mycobacterium avium paratuberculosis being shed by infected adult cows should take priority.;The NPV for the JD control program varied greatly across the herds. When calculated across all cows in the herd, the costs of the JD control programs implemented on these herds averaged... |
