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National surveillance for bovine spongiform encephalopathy (BSE) began in the Republic of Korea (ROK) in 1996. Surveillance programmes changed overtime to comply with the guidelines of the World Organisation for Animal Health (OIE). Bovine spongiform encephalopathy was designated as a notifiable disease in 1997. From July 2008, the BSE surveillance programme was intensified to test cattle in designated high-risk populations more effectively. New measures included the compulsory testing of all non-ambulatory cattle at abattoirs, and encouraging the testing of all dead cattle examined and recorded under the Mutual Aid Insurance Scheme (fallen stock). In addition, there was a vigorous search for animals suspected of being clinically infected. As a result, a total of 426,919 OIE points were achieved over a period of seven consecutive years to the end of October 2009. This enabled the submission of a successful application to the OIE in 2010 for recognition of the ROK's BSE disease status as being one of controlled risk, in accordance with Chapter 11.5. of the OIE Terrestrial Animal Health Code., (© World Organisation for Animal Health (OIE), 2012)

Despite various measures taken by the Japanese government to protect the cattle population from exposure to the bovine spongiform encephalopathy (BSE) agent, the first case of BSE was detected in September 2001. Subsequently, BSE surveillance was enhanced, involving mandatory reporting and investigation of all clinical BSE suspects, and testing of fallen stock and all cattle slaughtered for human consumption. Tests on over nine million cattle led to the detection of 35 additional cases by the end of May 2009. Using the surveillance data and other information as input variables, models were developed to explore the possible source of introduction of BSE into Japan, evaluate the effectiveness of control measures, estimate the prevalence of BSE in different birth cohorts, predict a future BSE epidemic, and simulate the impact of changes in surveillance strategies. Despite difficulties associated with the availability and uncertainty of some of the input variables, these models provided an objective insight into the BSE situation in Japan.

Epidemiological models have been used extensively as a tool in improving animal disease surveillance activities. A review of published papers identified three main groups of model applications: models for planning surveillance, models for evaluating the performance of surveillance systems and models for interpreting surveillance data as part of ongoing control or eradication programmes. Two Danish examples are outlined. The first illustrates how models were used in documenting country freedom from disease (trichinellosis) and the second demonstrates how models were of assistance in predicting the risk of future cases, detected and undetected, of a waning infection of bovine spongiform encephalopathy. Both studies were successful in advancing European policy changes to reduce the cost of surveillance to appropriate levels given the magnitude of the respective hazards.

Disease is often associated with debilitating clinical signs, disorders or production losses in animals and/or humans, leading to severe socio-economic repercussions. This explains the high priority that national health authorities and international organisations give to selecting control strategies for and the eradication of specific diseases. When a control strategy is selected and implemented, an effective method of evaluating its efficacy is through modelling. To illustrate the usefulness of models in evaluating control strategies, the authors describe several examples in detail, including three examples of classification and regression tree modelling to evaluate and improve the early detection of disease: West Nile fever in equids, bovine spongiform encephalopathy (BSE) and multifactorial diseases, such as colony collapse disorder (CCD) in the United States. Also examined are regression modelling to evaluate skin test practices and the efficacy of an awareness campaign for bovine tuberculosis (bTB); mechanistic modelling to monitor the progress of a control strategy for BSE; and statistical nationwide modelling to analyse the spatio-temporal dynamics of bTB and search for potential risk factors that could be used to target surveillance measures more effectively. In the accurate application of models, an interdisciplinary rather than a multidisciplinary approach is required, with the fewest assumptions possible.

Bovine spongiform encephalopathy (BSE) has presented serious challenges to both the World Organisation for Animal Health and national governments, in defining and implementing appropriate national control measures, and in agreeing trade rules that permit safe trade in cattle and bovine products. Precautionary trade rules were initially necessary, based upon the science of sheep scrapie, but research into BSE later enabled BSE-specific trade rules to be developed. As a result, current rules on trade are underpinned by a sound body of knowledge on BSE. Declining epidemics in most affected countries confirm the appropriateness of current precautions. Nevertheless, risk is primarily dependent on the prevalence of infection with BSE. In the face of low prevalence scenarios, certain precautionary measures in the Terrestrial Animal Health Code may now be considered excessive. A thorough review is therefore deemed appropriate.

Evaluating surveillance results is important in estimating the risk of bovine spongiform encephalopathy (BSE) cases in a particular country, or in countries from which products are imported. Although various methods have been proposed for quantitative evaluation of surveillance results, no methods focusing on surveillance from a qualitative perspective have yet been established. The authors have developed an objective method for evaluating the qualitative aspects of BSE surveillance, based on the analytic hierarchy process. Factors related to surveillance credibility were selected through expert meetings and arranged in a hierarchical structure. These evaluation factors were also weighted, so that a points system could be used for evaluation. As a result, 13 evaluation factors comprising three-layer hierarchies were generated. When surveillance in Japan before and after a BSE case was evaluated using this evaluation system, an improvement in the quality of the surveillance was observed after the outbreak. Although this study suggests that the selection of the experts had a significant effect on the outcome, the authors believe that this method will also be applicable for establishing qualitative evaluation systems for other diseases.

The authors present a basic quantitative spreadsheet model to evaluate the risk of bovine spongiform encephalopathy (BSE) within a national setting. The model is based on information from BSE risk assessments undertaken in Latin American countries. The analysis focuses on the level of regulatory implementation and its impact over different time periods and estimates the potential impact if one BSE-infected animal is introduced into the production cycle. The information is consolidated so that the results of the evaluation can be presented for a hypothetical country, 'Country X'. Evaluating the BSE cycle within a country may help in making decisions on where preventive or control measures should be placed and/or enforced. Such an evaluation may also be used as the exposure assessment of a risk assessment, recommended by the World Organisation for Animal Health to determine the BSE risk status of a given country.

On 10 September 2001, the first case of bovine spongiform encephalopathy (BSE) in Japan was confirmed in a five-year-old dairy cow born in Hokkaido and raised in Chiba prefecture. Subsequently, BSE surveillance was enhanced. As a result, 35 additional cases were detected by the end of March 2009, with two to ten cases being detected each year up to the end of 2007. The epidemic appeared to peak in 2006. Cases are detected mostly in dairy cattle; in cattle born in 1996 and 2000; and in cattle born in Hokkaido. Two were atypical cases of BSE and the remainder classical cases. This paper describes and discusses the demographic structure of dairy and beef cattle, surveillance programmes in place and the epidemiological features of the BSE epidemic in Japan.

The bovine spongiform encephalopathy (BSE) crisis clearly demonstrated the need to keep animal transmissible spongiform encephalopathies (TSE) under control in order to protect animal and human health. Scrapie is the most widespread TSE of livestock in the world. For this reason, health authorities in different countries have elaborated plans that aim towards scrapie eradication. The unusual nature of the scrapie agent and the fragmented status of scientific knowledge about it, along with the limitations of currently available diagnostic tools, make it unlikely that the objective of eradication will be achieved in the near future. Scientific research is focused on acquiring the knowledge that will improve the efficiency of these efforts.

The national risk of bovine spongiform encephalopathy (BSE) has not been assessed by many countries, and many countries are conducting little or no BSE surveillance. National measures implemented, including import restrictions, surveillance systems, and sanitary controls, should be based on actual BSE risk. Thus, as a first step, the national BSE status must be determined, particularly through assessment of the national risk. The World Organisation for Animal Health (OIE) provides recommendations for surveillance and risk assessment of BSE, which are considered the international standard by the World Trade Organization (WTO). This document describes the variables for determination of BSE status and gives guidance on specific options and practical considerations for meeting the BSE surveillance and risk assessment recommendations of the OIE.

The authors developed a mathematical model to assess the release risk of the bovine spongiform encephalopathy (BSE) agent into a country through the importation of live cattle, bone-in bovine meat and meat-and-bone meal (MBM) from the United Kingdom and other countries with BSE. Monte Carlo simulation was attempted using this model and input variables. The release risk in Japan, expressed as the weight of infected MBM released in Japan between 1993 and 2000, was estimated to be 23.4 kg to 53.8 kg. The simulation also indicated that imported MBM represented the most important risk factor for releasing the BSE agent into Japan. This paper also provides details of the first five cases of BSE detected in Japan between September 2001 and the end of 2002. In addition, the results of the investigation conducted to determine the source of infection and the measures taken by the Government of Japan to prevent the BSE agent from entering the food and feed chains are also outlined.

Bovine spongiform encephalopathy (BSE) was first described in the United Kingdom (UK) in November 1986. After the introduction of an active surveillance system, most countries in Europe have reported BSE cases in the cattle population. This indicates that the use of active surveillance in addition to passive surveillance is important to assess the true BSE status in a country. Scrapie, a transmissible spongiform encephalopathy (TSE) in sheep and goats, has been reported in countries throughout the world with a few notable exceptions. Concern was expressed that BSE could have been introduced into sheep and goats. Currently, distinguishing between scrapie and BSE in small ruminants is only possible through lengthy experiments in mice. Preliminary results of active surveillance, introduced in 2002, show that significant under-reporting occurred. The history of BSE in cattle shows that risk assessments concerning the risk in a given country were often ignored and subsequent risk management decisions were inaccurate, i.e. although the risk was probable, no measures were taken in terms of either animal or human health. Furthermore, the effect of the measures taken was often overestimated and these had to be amended several times. The most important action to prevent new cases of TSEs occurring is by banning the feeding meat-and-bone meal (MBM) to ruminants. Further measures to be considered are the exclusion of specified risk material and carcasses from rendering, the process parameters for rendering of animal waste and the prevention of cross-contamination of feed with MBM. The most important measures to protect the consumer are the ban on specified risk material, such as brain and spinal cord, which may contain particularly high concentrations of the BSE agent, and the ban on mechanically recovered meat. The most important measures taken in Europe and the scientific background thereof are described and discussed.

The Office International des Epizooties (OIE: World organisation for animal health) recommends that all OIE Member Countries determine the status of bovine spongiform encephalopathy (BSE) in their cattle populations by conducting a risk assessment and meeting certain BSE surveillance criteria. The OIE has identified and listed the factors and criteria for this in the International Animal Health Code. The factors to be assessed include the consumption of meat-and-bone meal (MBM) by cattle, the importation of cattle and MBM which are potentially infected or contaminated with the BSE agent, the livestock population structure, the rendering processes and the animal feeding practices. In this paper, the authors present an overview of these risk factors and criteria, detailing the relevant components of each. In the second part of this paper, the authors provide a risk assessment to demonstrate the application of the OIE BSE guidelines. This is a probabilistic risk assessment of the factors related to BSE for Canada which conforms to the OIE approach to import risk analysis. The steps include the hazard identification, release, exposure and consequence assessments and the risk estimation. A scenario tree for the release and exposure assessments was used to model the events emanating from the initiating failure event of importing cattle potentially infected with BSE. The consequence assessment describes the costs and losses associated with the introduction and establishment of BSE in other countries. The risk estimate, integrating the release, exposure and consequence assessments, indicates a negligible probability that BSE was introduced and established in Canada; nevertheless, the economic consequences would have been extreme.

The epidemic of bovine spongiform encephalopathy (BSE) in Europe in the late Twentieth Century required the interplay of two sets of factors, which now provide reference points for assessment of the BSE risk throughout the world. One set of factors consisted of the presence of infective agent in cattle or some other ruminant. The second set consisted of transmission and amplification of the disease, made possible through a particular feeding system that allowed persistent and habitual feeding of meat-and-bone meal (MBM) derived from cattle. The authors explore the ruminant production systems of three representative countries in South-East Asia against the background of factors required for the manifestation of BSE. The results can be extended to other countries in sub-tropical and tropical regions where similar, non-industrial ruminant production systems operate. In short, the lack of a nutritionally or economically rational niche for MBM as a source of dietary protein or nitrogen in many ruminant production systems removes the hazard of BSE.

Early epidemiological studies identified bovine spongiform encephalopathy as a feed-borne infection associated with infected meat-and-bone meal in animal feed. The infection may have derived from scrapie in sheep, a spontaneous genetic mutation in cattle, or a transmissible spongiform encephalopathy in another mammalian species. Experimental work on the risk of transmission has necessarily tried to identify risk materials and their infectivity levels, the nature and size of species barriers, the infectious dose, the route of infection, the strain of the agent and the genotype of the animals at risk. The identification of levels of infection in cattle tissues has aided the removal of risk materials from the human and animal food chains. Maternally associated transmission is unlikely to maintain an outbreak, but the offspring of clinical cases appear to be at greater risk when the rate of food-borne exposure is high. Studies of embryo transfer have not shown infection to be transmitted by this means. While the control measures appeared to be straightforward, compliance has at times proved difficult to enforce and quantify. This has necessitated more extensive prohibitions, aggressive enforcement and thorough auditing of compliance levels.

Bovine spongiform encephalopathy (BSE) is a neurodegenerative disease of cattle caused by prions that was first described in the United Kingdom (UK) in 1986. The BSE epizootic that commenced in the UK in the 1980s has since spread into other countries in Europe and Asia through exports of contaminated meat-and-bone meal or infected cattle. Over the past few years, other emerging or reemerging diseases have spread into previously free countries or regions through international trade. This negative effect of globalisation means that to implement successful preventive and strategic programmes to safeguard animal health, such programmes must, as a priority, take a regional approach. Global thinking, regional planning and local performance constitute the key factors for the successful control of animal diseases. In South America, initial preventive actions against BSE were adopted in 1989. Further measures adopted since then and based on new scientific and technical findings, have led to the demonstration that the region is free of BSE. These early preventive actions have reliably protected the region from importing BSE-infected material. An integral part of the project to determine the BSE status of South America was the training of personnel, the incorporation of technology and the provision of updated information through close relationships with international organisations and prominent international researcher workers. Regional activities aimed at harmonising BSE prevention programmes, producing objective and transparent data on the equivalence of regional BSE status and facilitating regional and international trade have recently been launched. Maintaining the BSE-free status of the region must be given high priority by the beef agro-industrial sectors.

As North American Free Trade Agreement partners, Canada, the United States of America (USA) and Mexico apply independent but harmonised transmissible spongiform encephalopathy (TSE) risk management strategies in observance of Office International des Epizooties guidelines. The divergence between bovine spongiform encephalopathy (BSE) risk management approaches in North American and Europe reflects comparatively reduced external and internal BSE risks in North America. The external quarantine and internal surveillance measures adopted for BSE respond to several iterations of national risk assessments initiated in the early 1990s and revised as recently as 2002. Feed bans applied since 1997 to preclude establishment of BSE also bear the potential to limit intra-species and inter-species exposure to scrapie, chronic wasting disease (CWD) and transmissible mink encephalopathy (TME). Surveillance continues for the four TSEs through collaborative efforts of national and sub-national veterinary infrastructures and accompanying laboratory networks. Mexico has never identified the presence of any TSE. The last diagnosed case of TME in North America dates back to 1985. Since the only recognised appearance in Canada through an import from Great Britain in 1993, BSE has not been detected in North America. Scrapie and CWD remain at generally low prevalence in Canada and the USA. Independent but harmonised eradication programmes target elimination of the latter two diseases.

The outbreak of bovine spongiform encephalopathy (BSE) and the discovery of the central role played by meat-and-bone meal (MBM) as the vehicle of infection resulted, from the late 1980s onwards, in the implementation of new regulations on the incorporation of animal proteins, and then of most fats of animal origin, into diets fed to ruminants and other farmed animals. The BSE-related feed ban, which has gradually been reinforced over time, has led to the investigation of cost-effective routes for adequately replacing MBM and tallow by new sources of dietary proteins, minerals and lipids in the formulation of manufactured concentrates. As far as the technical fulfilment of the nutritive requirements of growing and lactating ruminants is concerned, efficient alternative solutions, based principally on recourse to food materials from vegetals already exist or hopefully will soon be available in most of the situations prevailing in Europe. However, related aspects, such as animal feed-processing, availability and traceability of certain food materials, quality of animal products, environmental constraints or disposal of animal waste from the meat industry give cause for concern. The expected consequences of the BSE-related feeding regulations on the organisational and economic framework of animal and crop production sectors throughout Europe and at world level must also be evaluated.

A Veterinary Laboratory Service was commissioned by the Ministry of Agriculture, Fisheries and Food of the United Kingdom in 1894 and the Service commenced veterinary research in 1905. The Central Veterinary Laboratory (CVL) was opened in 1917 and has become known world-wide under the name 'Weybridge'. In 1922, a network of Veterinary Investigation Centres was established in England and Wales and these continue to make an important contribution to surveillance for animal diseases. Problems recognised at these centres provide an important stimulus for research at the CVL, a good example being the case of bovine spongiform encephalopathy (BSE). Research into many non-infectious and infectious diseases is conducted, and research into scrapie was already in progress when BSE was discovered in 1986. A research programme was commenced to investigate the clinical signs, diagnostic methods, pathology, pathogenesis and epidemiology of BSE and the transmission characteristics of the BSE agent in farm animals. Some of the results of these studies and prospects for the future are discussed.

The bovine spongiform encephalopathy (BSE) crisis in Member States of the European Union adversely affected beef consumption in Slovenia in 1996. Although the disease has not been reported in Slovenia to date, the controversy about the link between BSE and Creutzfeldt-Jakob disease and scandals related to the illegal trade in beef in some countries have triggered doubts among consumers. Beef consumption in Slovenia was estimated using a beef supply model, consisting of the following variables: purchase and slaughter of cattle and import and export of beef. The model estimated that beef consumption fell by 16% in 1996 compared with consumption in 1995. Approximately half of the reduction was compensated by an increase in consumption of pork and poultry meat.

The first case of bovine spongiform encephalopathy (BSE) in Switzerland was diagnosed in November 1990, although the risk factors identified in the United Kingdom were not all present in Switzerland. At 29 December 1998, a total of 282 BSE cases (all animals born in Switzerland), had been recorded. The number of cases is declining, with fourteen cases diagnosed in 1998 (at 29 December 1998). The measures taken are effective. However, the potential weakness in current activities that allow the disease to exist are being evaluated. Further measures to avoid even minimal risk for human and animal health will be taken if required. Experience gained from the past indicates that it is necessary to review the situation constantly and to inform the public and professionals regularly and in a transparent manner.

This paper reviews current knowledge on transmission of scrapie and bovine spongiform encephalopathy (BSE) by semen and embryos. In sheep, in particular, it is difficult to distinguish between the genetic transmission of susceptibility to scrapie and vertical transmission of the infection. Nevertheless, there is evidence that vertical transmission of infection does occur, probably across the placenta, but none to suggest a significant scrapie risk from semen. Two teams have studied scrapie transmission from experimentally infected sheep using embryo transfer. Whereas one team found no evidence for transmission, the results from the other team suggest that embryos, even after washing, might carry the disease into the offspring. In regard to goats, although genetic differences in susceptibility exist, they are much less obvious than in sheep. There is no evidence for vertical transmission or for transmission through semen and embryos. With regard to BSE, although it appears that genetic differences in susceptibility are absent or unimportant, some recent work does suggest that the disease may be passed from cow to calf. The route of transmission and stage or stages when this takes place are unclear, however. In conclusion, despite growing evidence to indicate that scrapie and BSE are unlikely to be transmitted through semen and embryos, more research is needed to confirm this. Furthermore, until all possibility of risk is ruled out, risk reduction methods must be considered, especially when semen and embryos are being imported into countries where the diseases do not exist.

Although bovine spongiform encephalopathy (BSE) has occurred in other European countries, the major epidemic has been in the United Kingdom (UK), where there have been more than 163,000 cases so far. BSE has been linked to the practice of feeding meat-and-bone meal (MBM), putatively contaminated with scrapie agent, to cattle. A ban on the feeding of MBM to ruminants in the UK has resulted in a significant decline in the number of reported cases. It is considered that BSE in other European countries probably originated through the use of British MBM in the diets of cattle in these affected countries. Recently, in the UK, a new variant form of Creutzfeldt-Jakob disease in humans has been discovered, which does not appear to have occurred before the advent of BSE. It may have been caused by BSE agent, possibly as a consequence of dietary exposure. The use of MBM in the diets of any livestock species has now been prohibited in the UK.

A specialist group of the Office International des Epizooties met in May 1996 to prepare updated information on bovine spongiform encephalopathy (BSE): in particular on the development of the epidemic, geographical incidence, nature of the disease, transmission, precautions and control measures. A revised Chapter 3.2.13. of the International Animal Health Code dealing with BSE, and an outline of the spongiform encephalopathies, are appended, along with a comprehensive bibliography.

Bovine spongiform encephalopathy (BSE) is a new disease of cattle first described in the United Kingdom in November 1986. BSE belongs to the scrapie-related group of diseases. The epidemiological studies performed in the United Kingdom demonstrate that the BSE epidemic was caused by feeding cattle with ruminant-derived protein contaminated by a scrapie-like agent. Until June 1994, the disease had been detected in indigenous cattle in Ireland, Switzerland and France. Three cases reported in Germany, two in the Sultanate of Oman, and single cases in the Falkland Islands (Islas Malvinas), Denmark, Portugal and Canada occurred in animals imported from the United Kingdom. Several countries have implemented surveillance programmes analysing the risk factors involved in the epidemic. An analysis of risk factors conducted in Argentina shows that it is highly unlikely that BSE or scrapie exist in the country, or will arise via feed in the future. As a continuation of the analysis of risk factors, a surveillance programme was implemented in the field and in abattoirs. Specialised personnel were trained in the clinical, histopathological and biochemical detection of the disease through a network of laboratories which covered 85% of the total cattle population and 100% of the high-risk group (dairy cows over five years of age). By using a statistical procedure with reference to the bovine population in nine provinces, 1,019 brains from animals belonging to the high-risk group were selected and studied by histopathological and biochemical analyses for BSE detection. The results were negative in all cases. It can be concluded from this analysis (with a sensitivity of detection of 2.95 per 1,000, and 95% statistical confidence) that Argentina may be regarded as BSE-free, and that the importation of infected animals or by-products may represent the sole potential source of introduction of BSE infection into the country in the future.

Epidemiological studies conducted in the United Kingdom have revealed the risk factors involved in the epidemic of bovine spongiform encephalopathy (BSE). This has facilitated a detailed study of risk factors associated with the possible introduction of BSE into Argentina. An analysis has been made of the numbers and geographical distribution of cattle in the country, the structure of the Veterinary Services responsible for controlling animal diseases, the way in which cattle and sheep are slaughtered, and the use of slaughter waste in the feed industry. The results of this analysis form the basis of a discussion of whether scrapie or BSE could become endemic in Argentina through contaminated feed or another route. The authors conclude that Argentina may be regarded as free from BSE, and that the importation of infected bovines is the sole potential risk for introduction of BSE in the future.

The first diagnosis of bovine spongiform encephalopathy (BSE) in the United Kingdom in 1986 was to stimulate the most intensive epidemiological study of any animal disease of all time in that country. It led also to the initiation of a broad-based research programme with an international flavour. This principally involved scientists and veterinarians in Europe (especially the United Kingdom) and the United States of America, especially those with experience of slow infections in general and experimental scrapie in particular. This final chapter highlights some of the significant discoveries made in the study of BSE and related diseases of this group but also emphasises the deficits in knowledge which need to be corrected before such diseases as scrapie in sheep and goats can be brought under control. The benefits resultant upon effective disease control will be manifest as improvement in animal production, welfare and, importantly, the removal of trading barriers currently in place to protect countries in which diseases such as BSE and scrapie do not exist. Of key importance is the development of a simple, cheap and effective diagnostic test for use in the live animal before the onset of clinical signs. This will be difficult since the nature of the causal agents is uncertain and none provokes either a detectable immune response or inflammatory reaction in the host. The earlier chapters, written by acknowledged specialists from around the world, deal with the specific diseases in detail and all present some of the most recent knowledge available. Here the authors emphasise the important role that major national and international agencies have in effecting the highest level of control possible in the absence of key information. International collaboration with countries in which these diseases exist, and as well as those where they are absent, is of paramount importance. It is essential that the BSE epidemic which has severely affected the cattle industry of the United Kingdom is not allowed to happen in developing countries. Whereas the former has implemented stringent control measures based on scientific knowledge and is well on the way to eradicating the disease, the latter could have much greater difficulty in establishing control. The answer is clear. BSE must be prevented from occurring elsewhere. To do that, knowledge of BSE and other members of the group should be widely dispersed and it is the purpose of this issue to do just that.

A detailed account is given of the occurrence of bovine spongiform encephalopathy (BSE), current research into the aetiology of this new disease of cattle, and the relationship between BSE, scrapie and other similar diseases. Epidemiology, clinical signs, pathology, diagnosis, prevention and control are described.