AJVR, Vol 66, No. 12, December 2005 2149 M ost international standards for sanitary measures for importation of animals and animal products depend on the disease status of the importing and exporting countries. Countries that wish to use mea- sures that result in a higher degree of protection than would be achieved by measures based on relevant international standards, guidelines, or recommenda- tions must provide a scientific justification. The documentation of freedom from infection is usually a prerequisite for such measures. Requirements for a country to establish freedom from infection to satisfy the sanitary and phytosanitary agreements are outlined in the World Organization for Animal Health guide- lines. 1 Typically, these requirements are based on the information contained in annual surveillance efforts. Definitive proof of the absence of infection or of the agent is virtually impossible to obtain. Therefore, proof is provided in terms of a science-based probability esti- mate that the infection of concern, if present, is below a specified acceptable prevalence. There are 2 fundamental objectives for the detec- tion component of a surveillance system for exotic dis- eases: early detection of newly introduced infection and documentation of freedom from infection. 2 Surveillance systems need to be based on epidemiolog- ic characteristics of the disease agent, economic impli- cations regarding trade and domestic production, herd demographics (size, breed, and age distribution), prevalence (between and within herds), test character- istics (sensitivity and specificity), and the clinical dis- ease picture, but they must meet the fundamental objectives. For short-incubation contagious diseases, this may mean intensifying surveillance to allow for timely recognition of infection before the problem becomes widespread. Denmark was declared free of infectious bovine rhinotracheitis (IBR) in 1991. Since 1991, there have been 6 introductions of IBR into Denmark, with the most notable occurring in 1995. In Denmark, a sero- logic surveillance program is used to screen for IBR. 3 The Danish IBR surveillance program was designed 20 years ago, when cattle demographics were different. The number of cattle herds has declined by 60% since 1982 to 23,031 in 2000, and the number of cattle has declined by 30% to 1.8 million in 2000. 4 The mean dairy herd size is now approximately 70 cows, an increase of 250%. 4 These demographic changes could substantially alter the probability of detecting an infected herd. For example, detection of infection in beef herds depends solely on slaughter surveillance. Small beef herds may irregularly send cattle to slaugh- ter, making it difficult to detect disease in a timely manner. Larger beef herds might send cattle to slaughter more regularly, which would increase the probability of detecting an infected herd. Despite these demographic changes, evaluation of the national IBR surveillance program has not been performed since implementation in 1991. Received January 5, 2005. Accepted March 30, 2005. From the Danish Dairy Board, Frederiks Alle 22, DK-8000 Aarhus C, Denmark (Chriel); Animal Population Health Institute, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80523-1681 (Salman); USDA, Animal and Plant Health Inspection Service, Veterinary Services, Centers for Epidemiology and Animal Health, 2150 Centre Ave, Fort Collins, CO 80526-8117 (Wagner). Supported by the Danish International EpiLab (journal No. 93S- 2466-Å02-01521). The authors thank Pam Timms for technical assistance. Address correspondence to Dr. Salman. Evaluation of surveillance and sample collection methods to document freedom from infectious bovine rhinotracheitis in cattle populations Mariann Chriel, DVM, PhD; M. D. Salman, BVMS, MPVM, PhD; Bruce A. Wagner, MS, PhD ObjectivesTo assess the sensitivity of the current surveillance program used in Denmark for detecting outbreaks of infectious bovine rhinotracheitis (IBR) at the herd level and to evaluate the impact of alterna- tive sample collection strategies on the sensitivity of the system in an acceptable time frame. Sample PopulationData from the Danish Central Husbandry Register on cattle of 24,355 and 25,233 beef herds and on 13,034 and 12,003 dairy herds in the years 2000 and 2001, respectively. ProceduresSurveillance programs were evaluated under current sample collection conditions and under 3 alternative scenarios by use of simulation modeling. Data from the current detection component of the surveillance system were used as input, taking into consideration the sensitivity and specificity of bulk- tank milk and serologic testing. ResultsThe current system identifies infected dairy herds within a 3-month period with desired accuracy largely because of the test characteristics and num- ber of bulk-tank milk samples. The system is less like- ly to detect infected beef herds in a timely manner because surveillance in beef herds depends solely on serologic testing at the time of slaughter. The effi- ciency of surveillance in dairy cattle herds was not decreased substantially when the slaughter-surveil- lance component was omitted. Conclusions and Clinical RelevanceGeograph- ically targeted sample collection during the high-risk season (winter) was predicted to increase the probabil- ity of rapid detection of IBR infection in cattle. This approach can be used for assessing other surveillance systems to determine the best strategies for detection of infected herds. (Am J Vet Res 2005;66:2149–2153)