| current value of historical and ongoing surveillance for disease freedom: surveillance for bovine johne's disease in western australia. | 'confidence' in freedom from disease is generally derived from multiple sources of varied surveillance information, and typically this surveillance evidence has been accumulated over time. in the state of western australia (wa) the main surveillance evidence supporting free zone status in the national bovine johne's disease (bjd) program comprises periodic surveys and the ongoing clinical diagnostic system. this paper illustrates a simple approach to current valuation of historical surveillance ... | 2008 | 18243373 |