Risk assessment for animal derived feedstuffs as vectors for bovine spongiform encephalopathy (BSE) in Germany. Part I: Comparative risk assessment for animal derived feedstuffs.

The occurrence of BSE cases in Germany after the ban of meat and bone meal for ruminant feed in 1994 requires a detailed investigation of animal deriv ed feedstuffs regarding their specific risks as vectors for the disease. Ac cepting the theory that BSE is a prion transmitted disease, the theoretical infectious potential was calculated for animal derived feedstuffs. This ca lculation was based on the assumption, that risk material (brain, spinal co rd) of one clinically diseased cattle was rendered in the process as establ ished in Germany (133 degreesC, 3 bar, 20 min) or, alternatively, that one diseased animal was slaughtered resulting in normal processing of the by-pr oducts for human food production. From this risk assessment it became obvio us that meat and bone meal was one, but probably not the most important sou rce for the spreading of BSE. Taking into account the high sensitivity of c alves it can be speculated that certain products, eg. from bone processing (bone meal) and fat melting (mixed animal fats), commonly used for the form ulation of milk replacers, might have been more important as pathways. As i t can't be excluded retrospectively that infected meat and bone meal was im ported from the UK, this non-calculable influence may have relativated the significance of the other products. The calculation model underlines that e fficient removal of specified risk material (brain, spinal cord) and adequa te processing (133 degreesC, 3 bar, 20 min) or alternatively other equivale nt treatments of fats are prerequisites for minimising the risk of feed bor ne transmission of BSE by animal derived feedstuffs. The epidemiological co nsequences are part of a subsequent paper.