Did UK 'dump' contaminated feed after ban?

The Risk of Prion Infection through Bovine Grafting Materials

BACKGROUND

Bovine-derived grafting materials are frequently used in a variety of bone augmentation techniques. The aim of this paper is to assess the unique safety issue of bovine-derived grafting materials that is rarely addressed in dental literature: risk of bovine spongiform encephalopathy (BSE).

METHODS

The validity of the current BSE diagnostic methods, surveillance and epidemiological trends in affected countries, and BSE infectivity in bovine bone before and after manufacturing processing were reviewed and analyzed.

RESULTS

Prion screening has significant limits. Humans are not safe from the infection of prion disease of other species. Prions can and do break the species barrier. There is evidence there may be tens of thousands of infectious carriers in the western countries alone. This raises concern about the potential for perpetuation of infection via medical procedures.

CONCLUSION

The limited ability to screen prions within the animal genome, along with a long latency period to manifestation of the disease (1 to over 50 years) in infected patients, provides a framework for discussing posible long-term risks of the xenografts that are used so extensively in dentistry. We suggest abolishing the use of bovine bone.

PCR identification of ruminant tissue in raw and heat-treated meat meals

To control the spread of bovine spongiform encephalopathy in cattle through contaminated animal feedstuffs, screening of feed products is essential. We designed five pairs of primers to identify specifically raw and heat-treated tissue from cattle, sheep, goat, deer, and ruminants in general. A forward common primer was designed based on a conserved DNA sequence in the mitochondrial 12S rRNA-tRNA(val)-16S rRNA gene, and reverse primers were designed to hybridize with a species-specific DNA sequence for each species considered. All primers were developed to create a specific PCR product small enough (less than 200 bp) to be suitable for heat-treated material. To evaluate the effect of heat treatment, a severe sterilization condition (133 degrees C at 300 kPa for 20 min) was chosen. Species-specific amplicons were obtained from all types of heat-treated meat meals. Analysis of laboratory-contaminated vegetable meals revealed that the detection limit of the assay was 0.05% for each species analyzed. This PCR-based analysis can be used as a routine method for detecting banned animal-derived ingredients in raw and heat-treated feedstuffs.

A quantitative assessment of the risk of exposure to bovine spongiform encephalopathy via meat-and-bone meal in Japan

The feeding of meat-and-bone meal (MBM) derived from cattle infected with bovine spongiform encephalopathy (BSE) is a major source of BSE infection. The risks of BSE infection via MBM in Japan were examined quantitatively to estimate infectivity to cattle via MBM derived from a single clinically infected animal being rendered. Three routes of exposure were modeled: (i) feeding cattle concentrates containing MBM as an ingredient, (ii) feeding cattle concentrates contaminated with MBM from non-ruminant feed at feed plants and (iii) directly feeding MBM in supplemental form to cattle on farms. The effectiveness of measures designed to restrict the feeding of ruminants with ruminant MBM (feed restriction) as well as differences in the risk of exposure among regions were examined using the model. The model revealed that the median total infectivity fed to dairy cattle via MBM derived from one infected animal was approximately 0.49 cattle oral ID(50) (5th percentile=0.43ID(50), 95th percentile=0.54ID(50)). This value was reduced by 55% after the addition of MBM to cattle concentrates was restricted in 1996. The risk of exposure in dairy cattle was twice that in beef cattle. Comparisons of regional differences in exposure risk indicated that the risk was highest in a region where 14 of the 20 BSE cases reported to date were born. Our model suggested that the routes of exposure via MBM were unlikely to result in increased propagation of BSE in Japan. Furthermore, despite some regional variation, the risk of exposure declined further after the feed restriction was imposed in 1996.

Trade related infections: farther, faster, quieter

Modern global trading traffics large volumes of diverse products rapidly to a broad geographic area of the world. When emergent infections enter this system in traded products their transmission is amplified. With truly novel emergent infections with long incubation periods, such as Human Immunodeficiency Virus (HIV) or variant Creutzfeld Jacob Disease (vCJD), this transmission may silently disseminate infection to far distant populations prior to detection. We describe the chronology of two such "stealth infections," vCJD and HIV, and the production, processing, and distribution changes that coincided with their emergence. The concept of "vector products" is introduced. A brief case study of HIV incursion in Japan is presented in illustration. Careful "multisectoral" analysis of such events can suggest ecologically critical pathways of emergence for further research. Such analyses emphasize the urgency of implementing safety measures when pathogens enter globally traded products.

A competitive polymerase chain reaction-based approach for the identification and semiquantification of mitochondrial DNA in differently heat-treated bovine meat and bone meal

The risk of bovine spongiform encephalopathy propagation was drastically reduced after the European Union (EU) Health Authorities adopted restrictions involving a ban on animal-derived proteins in the diet of farm animals. Currently, the EU's officially recommended method for controlling meat and bone meal (MBM) in animal feed is the microscopic method, which involves the identification of bone fragments on the basis of their morphological characteristics. Recently, we demonstrated that a polymerase chain reaction (PCR)-based assay can be used for the detection of taxon-specific DNA in MBM and animal feeds. To ensure the safe rendering of animal by-products, the EU Council requires that this material be treated at 133 degrees C at 300 kPa for 20 min. Here we investigate the relationship between DNA degradation, PCR amplification, and MBM heat treatment. With a competitive PCR-based approach, we compare the amplification efficiency of bovine mitochondrial DNA target sequences of different lengths in several heat-treated MBM samples. For our method, a synthetic competitive DNA is used as an internal control for both DNA extraction and PCR reaction. A correlation between an increase in treatment temperature and a reduction in the size of the target sequences suitable for amplification was observed, suggesting progressive DNA fragmentation due to the temperature. We show that short amplicons (147 bp) can be used to detect the presence of bovine mtDNA in MBM samples treated according to the current European regulations. The use of such a competitive approach to compare amplification efficiency levels of targets of different lengths might represent a useful tool for the determination of both the amount of MBM in animal feeds and its proper heat treatment.