Potential contamination of beef carcases with brain tissue at slaughter

Usage of meat and bone meal in animal, poultry and fish feeds: A survey and risk analysis for the occurrence of bovine spongiform encephalopathy in Bangladesh

BACKGROUND

Bovine spongiform encephalopathy (BSE) is an emerging zoonotic disease of cattle associated with pathological prion protein (PrP^sc ) transmitted via meat and bone meal (MBM). Although Bangladesh did not experience a BSE outbreak but the country could not export animal products to developed countries as has not yet been declared BSE free country by OIE due to lack of scientific risk evaluation for BSE. The objectives were identification of hazard, release and exposure pathways of pathological prion protein through MBM and analysis of risk for the occurrence of BSE in Bangladesh.

METHODS

The scientific data were reviewed, hazards were scheduled and surveys were conducted on livestock production system, import of MBM and its use to identify the hazards present in Bangladesh context. The analysis was done by the 'OIE Risk Analysis Framework 2006 and European Union (EU) Scientific Steering Committee (SSC) 2003'. From the historical reviews, import of MBM and its use was identified, as external hazards.

RESULTS

The analysis revealed that these hazards had negligible or moderate risk for the introduction of infectious PrP^sc as Bangladeshi cattle are vegetarian cattle. No milk replacer was used and use of slaughtered waste in the animal feed industry is absent. Unconsumable bones are processed to produce bone chips, fertilizers and bone meal for poultry feeds. Scrapie was never prevalent in Bangladesh. Therefore, risk from the internal challenge was negligible in Bangladesh for the occurrence of classical BSE. These prevented the propagation of BSE infectivity and eliminated BSE infectivity from the system very fast, if that was present.

CONCLUSIONS

It was concluded that introduction of PrP^sc into cattle population of Bangladesh through MBM was very negligible. Therefore, Bangladesh can be considered as BSE negligible risk country.

Welfare assessment of novel on-farm killing methods for poultry

There is a need for novel mechanical devices for dispatching poultry on farm following the introduction of EU Regulation (EC) no. 1099/2009 On the Protection of Animals at the Time of Killing. We examined three novel mechanical killing devices: Modified Armadillo, Modified Rabbit Zinger, a novel mechanical cervical dislocation device; and traditional manual cervical dislocation. The four killing methods were tested on 230 chickens across four batches. We measured behavioural, electroencephalogram and post-mortem outcomes in anesthetized laying hens and broilers at two life stages (juveniles and adults/slaughter age). Graeco Latin-Square designs systematically randomized killing treatment, bird type, age and kill order. All birds were lightly anaesthetized immediately prior to the killing treatment with inhalation of Sevoflurane. The novel mechanical cervical dislocation method had the highest kill success rate (single application attempt only, with no signs of recovery) of a mechanical method (96%). The Modified Armadillo was the least reliable with 49% kill success. Spectral analysis of electroencephalogram signals at 2 s intervals for successfully killed birds only revealed progressive decreases in median frequency alongside increases in total power. Later, total power decreased as the birds exhibited isoelectric electroencephalogram signal. Latencies to pre-defined spectral ranges associated with unconsciousness showed that birds subjected to manual and novel mechanical cervical dislocation achieved these states sooner than birds subjected to the modified Armadillo. Nevertheless all methods exhibited short latencies (<4 s). The Modified Rabbit Zinger had the shortest duration of reflex persistence for nictitating membrane, pupillary and rhythmic breathing post method application. Of the methods tested, the novel mechanical cervical dislocation device is the most promising mechanical method for killing poultry on-farm based on a range of behavioural, electroencephalogram and anatomical parameters. This device has the potential to fulfil the current need for a mechanical alternative to manual cervical dislocation.

On Farm Evaluation of a Novel Mechanical Cervical Dislocation Device for Poultry

Urgent development of alternative on-farm killing methods for poultry is required following the number restrictions placed on the use of traditional manual cervical dislocation by European Legislation (EU 1099/2009). Alternatives must be proven to be humane and, crucially, practical in commercial settings with multiple users. We assessed the performance and reliability of a novel mechanical cervical dislocation device (NMCD) compared to the traditional manual cervical dislocation (MCD) method. NMCD was based on a novel device consisting of a thin supportive glove and two moveable metal finger inserts designed to aid the twisting motion of cervical dislocation. We employed a 2 × 2 factorial design, with a total of eight stockworkers from broiler and layer units (four per farm) each killing 70 birds per method. A successful kill performance was defined as immediate absence of rhythmic breathing and nictitating membrane reflex; a detectable gap in the vertebrae and only one kill attempt (i.e., one stretch and twist motion). The mean stockworker kill performance was significantly higher for MCD (98.4 ± 0.5%) compared to NMCD (81.6 ± 1.8%). However, the MCD technique normally used by the stockworkers (based previous in-house training received) affected the performance of NMCD and was confounded by unit type (broilers), with the majority of broiler stockworkers trained in a non-standard technique, making adaption to the NMCD more difficult. The consistency of trauma induced by the killing methods (based on several post-mortem parameters) was higher with NMCD demonstrated by "gold standard" trauma achieved in 30.2% of birds, compared to 11.4% for MCD (e.g., dislocation higher up the cervical region of the spine i.e., between vertebrae C0-C1, ≥1 carotid arteries severed), suggesting it has the potential to improve welfare at killing. However, the results also suggest that the NMCD method requires further refinement and training optimization in order for it to be acceptable as an alternative across poultry industry, irrespective of previous MCD technique and training.

Alternative BSE risk assessment methodology for beef and beef offal imported into Japan

The Food Safety Commission (FSC) of Japan, established in July 2003, has its own initiative to conduct risk assessments on food stuffs known as "self-tasking assessment". Within this framework, the FSC decided to conduct a risk assessment of beef and beef offal imported into Japan from countries with no previous BSE reports; thus, a methodology was formed to suit to this purpose. This methodology was partly based on the previous assessments of Japanese domestic beef and beef imported from U.S.A./Canada, but some modifications were made. Other organizations' assessment methods, such as those used for BSE status assessment in live cattle by the OIE and EFSA's GBR, were also consulted. In this review, the authors introduce this alternative methodology, which reflects (1) the risk of live cattle in the assessed country including temporal risks of BSE invasion and domestic propagation, with the assessment results verified by surveillance data, and (2) the risk of beef and beef offal consisting of cumulative BSE risk by types of slaughtering and meat production processes implemented and the status of mechanically recovered meat production. Other possible influencing factors such as atypical BSE cases were also reviewed. The key characteristic of the current assessment is a combination of the time-sequential risk level of live cattle and qualitative risk level of meat production at present in an assessed country.

Electroencephalographic responses to concussive non-penetrative captive-bolt stunning in halothane - anaesthetised calves

AIM

To investigate the electroencephalographic (EEG) and cardiovascular responses of halothane-anaesthetised calves to non-penetrative captive-bolt stunning.

METHODS

Ten calves were minimally anaesthetised with halothane, using an established anaesthesia protocol. The EEG, blood pressure and electrocardiogram (ECG) were recorded before and after non-penetrative captive-bolt stunning. Visual inspection and alterations in the total power of the EEG (Ptot) were used to investigate the effects of stunning.

RESULTS

Captive-bolt stunning significantly altered cerebrocortical function in all animals. In four animals, Ptot decreased immediately following stunning and remained low throughout the recording period. In another five animals, Ptot responded to stunning in a biphasic manner characterised by an immediate decrease followed by a transient increase and then a final decrease to values similar to those of the non-biphasic animals.

CONCLUSIONS

Non-penetrative captive-bolt stunning significantly altered cerebrocortical function in halothane-anaesthetised calves. The changes in cerebrocortical function would be sufficient to produce insensibility within 0 to 14 seconds in conscious animals.

Comparison of analytical methods for the detection of central nervous system tissue in ground beef

Bovine spongiform encephalopathy is most likely transmitted by the consumption of central nervous system tissue of infected cows. The objective of this study was to compare the sensitivity or limits of detection of two central nervous system tissue detection assays (glial fibrillary acidic protein enzyme-linked immunosorbent assay [ELISA] and neuron-specific enolase Western blotting assay) in by-products and ground beef. By-products including brain, spinal cord, and ileum were collected from the slaughterhouse and used for analyses with ELISA and Western blotting assays. Beef samples were prepared by mixing ground beef with different amounts of spinal cord tissue (0, 0.03, 0.06, and 0.1%) and were analyzed using the two central nervous system tissue detection methods. Both analytical assays were applicable in detecting central nervous system tissue in ground beef. However, the ELISA method was considered superior because of its ease of use, high sensitivity, and rapidity as compared with the Western blot method.

Exposure assessment of TSEs from the landspreading of meat and bone meal

Recent changes in European legislation have meant that certain processed abattoir waste, which has been appropriately heat treated and ground to a specified particle size, can be spread on nonpasture agricultural land. This has opened the way for the potential landspreading of mammalian meat and bone meal (mMBM) derived from animals slaughtered for human consumption. This article reports on two separate case studies (Study 1 carried out in Great Britain (GB) and Study 2 carried out in Ireland) on the potential exposure to TSE infectivity following the spreading of abattoir waste (derived from animals slaughtered for human consumption) on nonpasture agricultural land. For Study 1, the average TSE infectivity on nonpasture agricultural land per year from sheep with scrapie was found to be higher (five orders of magnitude) than that estimated for BSE in cattle (3.9 x 10(-3) Ovine Oral ID(50)/ton of soil compared to 3.3 x 10(-8) Bovine Oral ID(50)/ton of soil). The mean estimate for BSE in sheep was 8.1 x 10(-6) Ovine Oral ID(50)/ton of soil. The mean level of infectivity in mMBM was assessed to be 1.2 x 10(-5) and 2.36 x 10(-5) ID(50)/ton of mMBM for Study 1 and 2, respectively. For Study 2 the spreading of mMBM was estimated to result in infectivity on nonpasture land of 1.62 x 10(-8) Bovine Oral ID(50)/m(3). The mean simulated probability of infection per year per bovine animal was 1.11 x 10(-9). Given the low infectivity density and corresponding low risks to bovines the spreading of mMBM could be considered a viable alternative for the utilization of mMBM.

Central Nervous System Tissue in Meat Products: An Evaluation of Risk, Prevention Strategies, and Testing Procedures

Since the outbreak of bovine spongiform encephalopathy (BSE) in the United Kingdom in 1986 and its subsequent link to the human neurological disorder variant Creutzfeldt-Jakob disease (vCJD), presence of tissues from the central nervous system (CNS) in meat products has been considered a public health concern and, thus, has been banned from entering the human food chain in many countries. Despite this, potential can exist during harvesting to contaminate or cross-contaminate edible meat products with CNS tissue that is designated as a specified risk material (SRM) in many countries. Methods used to detect CNS tissue in meat products vary greatly in their sensitivity, specificity, cost, labor and expertise needed, ease of completion, and type of results given (qualitative vs quantitative) and, within these constraints, appropriate testing methods must be selected to monitor or verify that meat products system controls are effective in removing CNS tissue from the human food chain. The extent to which monitoring procedures are needed should be based on the public health risk of CNS tissue in meat products as determined by each sovereign nation and/or third-party international organizations such as the World Organization for Animal Health (OIE). Risk associated with consumption of CNS tissue should be estimated by sovereign nations by establishing prevalence of BSE within their borders. Using this information, science-based decisions may guide international policy and trade. Using available scientific information, appropriate testing methods for monitoring or verification, and prevalence information, nations can estimate and reduce, to the extent deemed necessary, the public health risk of vCJD.

Detection of central nervous system tissue on meat and carcass-splitting band saw blade surfaces using modified fluorescent glial fibrillary acidic protein enzyme-linked immunosorbent assay sampling and extraction procedures

This study was conducted to determine optimal buffer pH, extraction procedure, and temperature for detecting central nervous system (CNS) tissue on meat surfaces and on carcass-splitting band saw blades using swab sampling. Glial fibrillary acidic protein (GFAP) is restricted to CNS tissue and has been used as a marker for CNS tissue presence in meat products. Sample preparation, extraction procedure, and extraction temperature of glial fibrillary acidic protein fluorescent enzyme-linked immunosorbent assay (GFAP F-ELISA) were modified to detect CNS tissue on meat surfaces and on carcass-splitting band saw blades. Maximum GFAP recovery was observed with an extraction buffer pH of 7.4. Extracting samples at room temperature by vortexing for 30 s in 1 ml of extraction buffer (phosphate-buffered saline [pH 7.4] plus 0.05% sodium dodecyl sulfate) consistently provided detection of GFAP on meat surfaces contaminated with 500 microg of spinal cord suspension per 50 cm2 and on carcass-splitting band saw blades contaminated with 20 microg of spinal cord suspension per 50 cm2. Recovery of GFAP was not affected by storing samples overnight at 4 degrees C. The current studies demonstrate the effectiveness of modified sampling procedures and preparations, sample extraction buffer pH, and extraction temperatures. These modifications introduced to the original F-ELISA sampling protocol result in asensitive and repeatable assay for detection of CNS tissue on meat surfaces and on carcass-splitting band saw blades.

Comparison of immunochemical (enzyme-linked immunosorbent assay) and immunohistochemical methods for the detection of central nervous system tissue in meat products

Three methods are widely used in the United States to detect the presence of central nervous system (CNS) tissue in meat products: the fluorescent enzyme-linked immunosorbent assay (F-ELISA), developed in this laboratory, the colorimetric Ridascreen Risk Material 10/5 ELISA (R-ELISA), and the U.S. Department of Agriculture, Food Safety and Inspection Service immunohistochemical (IHC) procedure. These assays are based on the immunological detection of glial fibrillary acidic protein (GFAP), a neural antigen largely restricted to the CNS. The objective of the current study was to compare the sensitivity and repeatability of these tests for detecting the presence of neural tissue in meat. Ground beef spiked with 0.05 to 0.5% of bovine brain, spinal cord (SC), or dorsal root ganglia, as well as advanced meat recovery samples, were evaluated by each of the three GFAP detection procedures. Interassay coefficients of variation for the F-ELISA GFAP standards were 7 to 25%, and intra-assay variation due to sampling and extraction of spiked ground beef was 7 to 13% for SC and 8 to 14% for brain (n = 10). The F-ELISA was the most sensitive of the methods tested, capable of detecting 0.3 ng GFAP standard per well and the presence of 0.05% brain and SC in meat. The R-ELISA standards produced highly variable results (up to 36% variation) and, as a result, none of these standards were different from zero (n = 26). The R-ELISA resulted in high sample variation in SC-spiked ground beef samples (coefficients of variation were 23 to 50%) and did not detect the presence of brain contamination. After modification of the R-ELISA sampling and extraction methods, SC-spiked sample variation was reduced to 16 to 20%, and sensitivity was improved from 0.3 to 0.2% SC, although brain tissue was still not detected. The IHC analysis of CNS-adulterated ground beef had a sensitivity of 0.2% SC and 0.05% brain, with false-negative rates of 10 to 20% at and above the stated sensitivities. None of the methods examined detected dorsal root ganglia contamination. The F-ELISA detected the presence of CNS contamination in 20% of the advanced meat recovery samples, compared to 3.5 to 5% for the R-ELISA and 2% for IHC. This study suggests that the F-ELISA is much more sensitive and repeatable than either the R-ELISA or the IHC procedure method for the detection of CNS tissue in meat products.

Detection of bovine central nervous system tissue in liver sausages using a reverse transcriptase PCR technique and a commercial enzyme-linked immunosorbent assay

The suitability of a reverse transcriptase (RT) PCR assay was evaluated for the detection of bovine central nervous system (CNS) tissue specifically in liver sausages. Because of its emulsifying effect, CNS tissue was frequently added to this kind of meat product in the past. On standard samples, the RT-PCR technique reliably detected a concentration of 0.25% bovine CNS tissue in liver sausages stored for up to 28 days. Following the successful application of RT-PCR for the detection of bovine CNS tissue in these specially prepared samples, a field study was performed with a total of 258 liver sausages purchased in retail markets. All sausages were tested with both an RT-PCR assay and a commercial enzyme-linked immunosorbent assay (ELISA) kit. Nine (3.5%) of the retail liver sausage samples were positive for CNS tissue in the ELISA, but none were positive for this tissue in the RT-PCR assay. All positive ELISA results indicated the presence of 0.23 to 0.30% CNS tissue. Recent studies have indicated that the RT-PCR assay is not as sensitive for porcine CNS tissue as for bovine CNS tissue, which this assay can detect at 0.25%. Although the ELISA is not species specific, the CNS tissue detected by the ELISA is assumed to stem from a nonbovine species. The RT-PCR technique is a sensitive tool for the detection of bovine CNS tissues in a problematic matrix such as liver sausage. ELISA screening followed by a species-specific RT-PCR assay for bovine CNS tissue is a practical approach for monitoring meat products for compliance with European food regulations.

Brain tissue fragments in jugular vein blood of cattle stunned by use of penetrating or nonpenetrating captive bolt guns

Although the incidence of bovine spongiform encephalopathy in cattle continues to decline in the United Kingdom, it remains important to maintain vigilance of all potential routes of transmission of infection to humans. Initial studies have demonstrated a potential risk of carcass contamination with brain tissue following the use of captive bolt gun stunning in cattle. The objective of this study was to further explore these initial findings particularly in regard to captive bolt guns currently in use in the United Kingdom. Brain tissue fragments or elevated levels of a marker protein for brain tissue were detected in venous blood samples from 4% (95% confidence interval, 1.6 to 9.8%) of cattle stunned by penetrating captive bolt gun and from 2% (95% confidence interval, 0.6 to 7%) of those stunned by nonpenetrating captive bolt gun.

Transfer of spinal cord material to subsequent bovine carcasses at splitting

During the slaughter process, cattle carcasses are split by sawing centrally down the vertebral column, resulting in contamination of each half with spinal cord material. Using a novel method based on a real-time PCR assay, we measured saw-mediated tissue transfer among carcasses. Up to 2.5% of the tissue recovered from each of the five subsequent carcasses by swabbing the split vertebral face came from the first carcass to be split; approximately 9 mg was spinal cord tissue. Under controlled conditions in an experimental abattoir, between 23 and 135 g of tissue accumulated in the saw after splitting five to eight carcasses. Of the total tissue recovered, between 10 and 15% originated from the first carcass, and between 7 and 61 mg was spinal cord tissue from the first carcass. At commercial plants in the United Kingdom, between 6 and 101 g of tissue was recovered from the saw, depending on the particular saw-washing procedure and number of carcasses processed. Therefore, if a carcass infected with bovine spongiform encephalopathy were to enter the slaughter line, the main risk of subsequent carcass contamination would come from the tissue debris that accumulates in the splitting saw. This work highlights the importance of effective saw cleaning and indicates that design modifications are required to minimize the accumulation of spinal cord tissue debris and, hence, the risk of cross-contamination of carcasses.

Dissemination of brain emboli following captive bolt stunning of sheep: capacity for entry into the systemic arterial circulation

The epidemic of bovine spongiform encephalopathy in the United Kingdom and the recognition of a variant of Creutzfeldt-Jakob disease prompted revision of the guidelines for slaughter of cattle and sheep to prevent contamination of the edible parts of the carcass with central nervous system tissue. We previously showed that captive bolt gun stunning, which is routinely used for the slaughter of cattle and sheep, causes entry of fragments of central nervous system tissue into the jugular vein. To determine whether such tissue can traverse pulmonary capillaries to enter the systemic circulation, we introduced small volumes of brain tissue that had been disrupted by stunning with a captive bolt gun into the jugular vein of sheep sent for slaughter. We examined aortic blood samples by immunocytochemistry for neurofilament and S100 proteins and by enzyme-linked immunosorbent assay for glial fibrillary acidic protein and found fragments of neurofilament- and S100-immunopositive central nervous system tissue in samples from 2 of 11 sheep and elevated glial fibrillary acidic protein in 6 sheep. Our findings suggest that central nervous system tissue that is dislodged during routine captive bolt gun stunning and slaughter of sheep can enter the systemic arterial circulation and that, in some cases, this method of slaughter of an animal infected with bovine spongiform encephalopathy would be likely to contaminate edible parts of the carcass with infective material.

Dissemination of central nervous system tissue during the slaughter of cattle in three Irish abattoirs

Sponge samples were taken from the carcases, meat, personnel and surfaces involved in stunning, slaughter and dressing/boning activities at three abattoirs, and from retail beef products. The samples were examined for the presence of central nervous system (CNS)-specific proteins (syntaxin 1B and/or glial fibrillary acidic protein (GFAP), as indicators of contamination with CNS tissue. Syntaxin 1B and GFAP were detected in many of the sponge samples taken along the slaughter line and in the chill rooms of all three abattoirs; GFAP was also detected in one sample of longissimus muscle (striploin) taken in the boning hall of one of the abattoirs but not in the other two abattoirs or in retail meats.

Comparative evaluation of the performance of two commercial kits for the detection of central nervous system tissue in meat

The ScheBo Brainostic test, which detects neuron-specific enolase by Western blotting, and the r-Biopharm Ridascreen Risk Material ELISA test, which detects the presence of glial fibrillary acidic protein, were evaluated using meats containing spinal cord and brain central nervous system (CNS) tissue from ovine and bovine species. The meats were pork, cooked pork sausage, raw minced lamb and cooked minced lamb. Spiking of the CNS tissue ranged from 0.01 to 5%. No false-positives were observed with either test using the manufacturers' analytical protocols. The presence or absence of CNS tissue was correctly determined in 20 of 20 samples using the ScheBo Brainostic test and 18 of 20 samples using the Ridascreen tests. When results were placed in categories according to quantity of CNS tissue detected, 19 of 20 samples were classified correctly using the Brainostic test and 14 of 20 samples using the Ridascreen test. Both kits were considered appropriate for reporting the presence of 1% or more CNS tissue in meat products, but the ScheBo Brainostic test was more consistent at detecting the presence of CNS tissues below the 1% level. Overall, the format of the Ridascreen test was technically easier to use, and the data simpler to interpret.

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

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.

The detection of central nervous system tissue on beef carcasses and in comminuted beef

We report the development and validation of a fluorescent enzyme-linked immunosorbent assay (ELISA) for glial fibrillary acidic protein (GFAP), which can be used as a rapid and sensitive method to detect CNS tissue in meat products. The fluorometric assay is sensitive to 0.2 ng GFAP and has an intra-assay coefficient of variation (CV) of 2.0% and an interassay CV of 14.1%. Bovine spinal cord and brain demonstrate dose-response curves that are parallel to GFAP standards, whereas peripheral sciatic nerve and cervical ganglia also cross-react at high tissue levels. The use of another central nervous system marker, syntaxin 1-B, was not effective for neural tissue detection. Less than 1.0 ng GFAP per mg tissue was found on most beef subprimals and advanced meat recovery (AMR) product. Occasional samples contained higher levels of GFAP, probably because of contamination by the carcass-splitting saw, incomplete removal of the spinal cord, or a chance sampling of a major nerve. Further reduction of CNS content was facilitated by removal of the cervical vertebrae and the spinal canal prior to processing beef chuck bones through AMR equipment. The presence of GFAP was very low (0.037 ng/mg) in beef patties collected from major processors throughout the USA. The presence of normal sausage ingredients or heating the product to 80 degrees C for 60 min did not affect the detection of GFAP. Heating the product to 115 degrees C for 100 min eliminated the detectability of GFAP.

Bovine spongiform encephalopathy and variant Creutzfeldt-Jakob disease: implications for Australia

The bovine spongiform encephalopathy (BSE) epizootic developed in the United Kingdom in the mid-1980s. Feeding practices in the cattle industry amplified the causative prion, and meat contaminated with BSE entered the market. Human consumption of prion-contaminated meat led to the new zoonosis--variant Creutzfeldt-Jakob disease (vCJD). The UK BSE Inquiry published its report in October 2000; while praising policy decisions, it also documented failures in the execution of these policies, specifically delays and lack of rigour. Australia is in an excellent position to maintain its BSE- and scrapie-free status, but widespread active surveillance of neural and non-neural tissue from all species of farmed quadrupeds is needed.

Jugular venous emboli of brain tissue induced in sheep by the use of captive bolt guns

Emboli of central nervous tissue were detected in the jugular venous blood of two of 15 sheep stunned with a conventional cartridge-operated captive bolt gun and in two of 15 sheep stunned with a pneumatically activated gun. No emboli were detected in arterial blood from these sheep or in venous blood from sheep stunned electrically. Emboli from an animal with BSE could transmit the disease to people.

Methods for detection of haematogenous dissemination of brain tissue after stunning of cattle with captive bolt guns

Because of concern that the stunning of cattle with captive bolt guns (CBGs) could, if used on an animal with bovine spongiform encephalopathy (BSE), cause embolism of infective brain tissue and carcass contamination, the Ministry of Agriculture, Food and Fisheries commissioned research to assess the risk of haematogenous dissemination of CNS material after stunning. We have devised two methods to investigate this risk. The first involves the concentration of embolic tissue in buffy coat Cytoblocks that can be embedded for sectioning, microscopy and immunocytochemistry. The second method is an ELISA for the presynaptic protein, syntaxin 1B. The methods were validated by analysis of several bovine tissues, including blood samples deliberately contaminated with brain. We then studied jugular venous blood obtained before and after the stunning of 60 cattle with CBGs. Samples obtained, after stunning, from five of the cattle contained CNS tissue within the Cytoblocks and yielded positive syntaxin assays. Syntaxin was also detected in samples from one other animal that had been stunned with a pneumatically operated CBG. The described methods should allow an assessment of the risk of neuroembolism associated with different types of CBG and may also be useful in other contexts.

Observations on the trajectory of the bullet in 15 horses euthanased by free bullet

The trajectories taken by the free bullets used to euthanase 15 horses were examined. The point of entry of the bullet relative to the recommended site was measured, together with the angle of the trajectory of the bullet relative to a tangent to its point of entry, the deviation of the trajectory from the midline of the brain, the structures of the brain that were damaged and the extent of this damage. Despite a reasonably consistent point of entry, there were wide variations in the damage inflicted, ranging from the total destruction of the hindbrain to injury to the cerebral cortex alone. The extent of the bullet's lateral deviation from the midline appeared to be the most significant factor affecting the level of destruction to the hindbrain, suggesting that angular direction may be more important than precise surface location in effecting a satisfactory kill.