Estimation of the Number of the Cattle Infected with BSE Prion Protein Using BSurvE Method

Abstract

Bovine spongiform encephalopathy (BSE) is the disease which causes spongiform pathologic change in the brain tissues. It has been concerned that there is the possible link between BSE and variant Creutzfeldt-Jacob disease. Then, BSE is now recognized as a significant zoonotic disease. In Japan, the first BSE case was detected in September 10th, 2001, and as of December 2007, 33 BSE cases were detected. In this study, we estimated the number of the BSE-infected animals by using the BSurvE method.
In the estimation, we used the number of the tested animals and the number of the test-positive animals which both were collected in abbatoirs and farms. In order to reflect the actual conditions of the Japanese BSE testing program, we modified the original BSurvE model into the Japanese specifications. The main modification was the reduction of the number of the surveillance streams from four to three by omitting the stream of the clinical suspects.
The main result was that as of the end of 2006, 7 BSE infected animals were remaining in Japan. These 7 infected animals consisted of : one born in 1999, three born in 2000, one born in 2001 and two born in 2002. The numbers of the total infected animals in each cohort were also estimated. The result showed that the highest exposure had occurred in 1996, and the estimated BSE-infected animals were 288. The estimation also showed that the BSE-infected animals born in 2000 were 69. This was the second highest level of the exposure.