Studies on contamination of beef with tissues of the central nervous system (CNS) as pertaining to slaughtering technology and human BSE-exposure risk.

Contamination of beef by tissues of the central nervous system (CNS) due to slaughter technology causes some concern considering the potential health hazard by food borne exposure to the infectious agent of BSE. The present study was designed to quantify the extent of CNS contamination as pertaining to stunning and splitting technology. Of the 726 animals 48 contained a total of 58 emboli-like particles in lungs and/or right ventricles. The incidence of emboli-like particles was found to be slightly higher in animals slaughtered without pithing (5.9%) than in the animals slaughtered with pithing (4.1%). Of the 58 emboli-like particles only two were positive in the anti-NSE western immunoblotting (0.3% of the 726 animals). The immuno reaction of these NSE-positive particles was several orders of magnitude lower as obtained by pure brain material. The microscopical analysis of the two NSE-positive emboli-like particles for presence of CNS-like tissues was negative. Following splitting of carcasses by sawing with and without prior removing the spinal cord we found NSE-positive reactions in 32% and 17% of the samples, respectively. The immuno reaction, however, was predominantly comparable to standard material containing less than 0.5% CNS. Overall the results show that CNS contamination of bovine carcasses cannot be excluded by current slaughter technology. However, the additional human BSE-exposure risk can be judged to be at least minor when considering extent of contamination, dilution effects and BSE-testing.