In February 2006 the Danish Cattle Federation initiated a national voluntary control programme "Operation Paratuberculosis" ("Operation PTB"). The programme focuses on closing transmission routes, because it has been demonstrated to be essential for the control of paratuberculosis in cattle herds. However, closing transmission routes is also difficult to practice, because persistence and much extra labour is needed. This amount of labour is reduced in "Operation PTB" which implies diagnostics of all cows 3-4 times per year by milk-ELISA, and - in cooperation with the herd health advisor - a contingency plan for changes in management and housing systems is made in order to reduce transmission of PTB. Transmission routes between calves and all cows being diagnosed as infectious should be broken effectively, and the most infectious cows culled before the next calving. The improvement of management is thus focused only on cows having been diagnosed as infectious instead of on the whole herd. Thereby the labour and time needed for improving management are reduced considerably.

The expected long-term effects of this strategy compared to alternative strategies were evaluated by simulation studies with the herd-simulation model PTB-Simherd. Scenarios were simulated in a herd with 200 cows (500 replications), an initial herd prevalence of 25% and an otherwise typical Danish herd management.

The simulated results of following "Operation PTB" were a reduction of prevalence from 25% to 5% after 5 years and less than 1% after 8 years, which makes this strategy just as effective in reducing prevalence as if management had been optimized for all cows in the herd. If no action was taken to control PTB, the prevalence would increase to 75% after 10 years. If transmission routes were not broken by improving management, but infectious cows were still culled within the next calving, the prevalence continued to increase to 26-39% depending on how quickly the infectious cows were culled after having the diagnosis. The economy of "operation PTB" compared to the economy of optimizing the management of all cows (which implies more labour hours, but no costs for tests) depends directly on the hourly rate and the time spent on optimizing management. If the extra workload per calving is assumed to be 1 hour, "Operation PTB" is the economically most attractive option in Denmark whenever the hourly rate exceeds 7 € (9 $).