Use of a Marker Organism To Model the Spread of Central Nervous System Tissue in Cattle and the Abattoir Environment during Commercial Stunning and Carcass Dressing

Abstract

Due to concerns about a link between variant Creutzfeldt-Jakob disease in humans and similar prion protein-induced disease in cattle, i.e., bovine spongiform encephalopathy (BSE), strict controls are in place to exclude BSE-positive animals and/or specified risk materials including bovine central nervous system (CNS) tissue from the human food chain. However, current slaughter practice, using captive bolt guns, may induce disruption of brain tissues and mobilize CNS tissues into the bovine circulatory system, leading to the dispersion of CNS tissues (including prion proteins) throughout the derived carcass. This project used a marker (antibiotic-resistant) strain of Pseudomonas fluorescens to model the effects of commercial captive bolt stunning procedures on the movement of mobilized CNS material within slaughtered animals and the abattoir environment. The marker organism, introduced by injection through the bolt entry aperture or directly using a cartridge-fired captive bolt, was detected in the slaughter environment immediately after stunning and in the abattoir environment at each subsequent stage of the slaughter-dressing process. The marker organism was also detected on the hands of operatives; on slaughter equipment; and in samples of blood, organs, and musculature of inoculated animals. There were no significant differences between the results obtained by the two inoculation methods (P < 0.05). This study demonstrates that material present in, or introduced into, the CNS of cattle during commercial captive bolt stunning may become widely dispersed across the many animate and inanimate elements of the slaughter-dressing environment and within derived carcasses including meat entering the human food chain.

Risk Factors and Control Measures for Bacterial Contamination in the Bovine Meat Chain: A Review on Salmonella and Pathogenic E.coli

“…When the same pistol was then used to stun subsequent healthy sheep, marked organisms were found in the blood of 30% to 40% of the animal carcasses. Similar findings were reported by Daly et al (2002) after inoculation of a marker strain of Ps. fluorescens into the central nervous system of cattle.…”

“…During the mentioned studies Daly et al, 2002), the levels of bacteria inoculated experimentally into the brain were relatively higher comparatively to the levels of bacteria commonly reported in slaughterhouses; suggesting that the risk of transmitting pathogens through the stun wound would be much lower under commercial conditions. However, as it known that Salmonella and pathogenic E. coli require low infective doses (Blaser & Newman, 1982;Coia, 1998) the risk should be considered as significant.…”

Spread and Control of Prion Diseases in the Food and Feed Chains

“…[58] Perhaps most worryingly, the marker organisms were found in the air, and on the hands and aprons of the operator. [58] In another similar study, [57] the marker organism P. fluorescens was detected in the slaughter environment immediately after stunning and at each subsequent stage of the slaughterdressing process, including on the hands of the operators, the slaughter equipment (captive bolt gun and knife), the cattle hide, and the carcass splitting saw.…”

“…[43] In a study designed to trace the spread of CNS tissue in the cattle body after stunning with a cartridge-fired stunner, a marker microorganism, Pseudomonas fluorescens, was inoculated into the bovine brain via the stunning procedure. [57] The researchers reported finding this bacterium in the animal's blood, spleen, liver, kidney, lymph node, lung, and spinal cord. Using a similar approach, two microorganisms, Escherichia coli and P. fluorescens, have been detected in the blood, liver, lung, spleen, lymph node, longissimus muscle, and on the carcass surface of stunned sheep.…”

Opinion of the Scientific Panel on biological hazards (BIOHAZ) on BSE risk from dissemination of brain particles in blood and carcass following stunning

“…The markers were either smeared on the bolt before shooting, or applied on the skin at the shooting point before stunning. Using air samplers and swabs, the markers could be detected in the environment and on hands and apron of the operators (Buncic et al, 2002;Helps et al, 2002;Daly et al, 2001; http://www.efsa.eu.int dissemination of brain particles in blood and carcass following stunning al., 2004). These results, although indirectly, indicate to possibility of increased exposure of the abattoir environment and the staff to CNS particles.…”