BSE, feed and cattle in Switzerland: Is there a spatial relation?Heinzpeter Schwermera, Katharina Forstera, Franz Brülisauera, Claude Chaubertb and Dagmar Heima
a Swiss Federal Veterinary Office, Schwarzenburgstrasse 155, 3003 Bern-Liebefeld, Switzerland
b Federal Research Station for Animal Production (RAP), Tioleyre 4, 1725 Posieux, Switzerland
(Received 20 July 2006; accepted 4 December 2006; published online 13 March 2007)
Abstract - Cross-contamination of cattle feed with meat and bone meal (MBM) allowed in feed for other species is regarded as the current hypothesis for the infection pathway of Bovine Spongiform Encephalopathy (BSE) cases occurring after the implementation of a ban on feeding MBM to cattle. This study was aimed at establishing a spatial relation between BSE cases in Switzerland and the findings of MBM in cattle feed. A cluster analysis and a cohort study were performed. Two hundred sixteen BSE cases born after December 1990 and detected until August 1st 2005, screening data of 504 feed producers between 1996 and 2001 and population data from the Swiss 2001 cattle census were included. The cluster analysis showed feed producer, positive for MBM contaminations in cattle feed, as possible cluster centres for BSE cases. In the cohort study, farms within a radius of 2 and 10 km around positive feed producers showed significantly higher odds to have a BSE case than the control group. The odds ratio and its 95% confidence interval were 2.23 (1.26-3.93) for the 2 km radius and 1.38 (1-1.9) for the 10 km radius. The results provide evidence for a spatial relation between cross-contamination and BSE occurrence. These findings support the hypothesis of cross-contamination to be an important route for BSE transmission after a feed ban.
Key words: bovine spongiform encephalopathy / compound feed / cluster / spatial analysis / feed producer
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© INRA, EDP Sciences 2007