A model to assess the risk of the introduction into Japan of the bovine spongiform encephalopathy agent through imported animals, meat and meat-and-bone meal.

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.