Scientific and technical assistance on the minimum sample size to test should an annual BSE statistical testing regime be authorised in healthy slaughtered cattle

This Scientific Report of EFSA provides scientific and technical assistance to the European Commission on (i) the minimum sample size to test, should an annual Bovine Spongiform Encephalopathy (BSE) statistical regime be authorised in healthy slaughtered cattle in certain EU Member States (MSs), and (ii) on the added value of that sample size for monitoring the trend of Classical BSE, Atypical BSE, and the emergence of a hypothetical new type of cattle Transmissible Spongiform Encephalopathy (TSE). Firstly, an evaluation of the epidemiological trends of BSE in 25 EU MSs was carried out in groups based on historical BSE monitoring data. Secondly, and with the aid of a purpose-built model called Cattle TSE Monitoring Model (C-TSEMM) developed by an EFSA contractor, both the assessment of the design prevalence and of the sensitivity of different BSE monitoring scenarios were carried out. Among the assumptions made in the C-TSEMM, a key one is that for those EU MSs with no, or few, BSE cases post-2001 an alternative estimate of cohort-based prevalence is required. This is estimated based on the average prevalence of the group of MSs with BSE cases under which they were placed in previous EFSA Opinions. Also, the model estimates presented are based on the demographics of the adult cattle population and on the number of adult cattle removed from the population via the different streams in 2011 (i.e. healthy slaughter, animals showing clinical signs of disease during ante mortem inspection, emergency slaughtered animals and fallen stock). Therefore, future fluctuations in those numbers at EU level and in each of the MSs will impact on the validity of the estimates presented in this report. A series of recommendations are made on sampling strategies for BSE monitoring and on the future use of the C-TSEMM.