Presentation on theme: "Current Issues in Food BSE Claire Appleton and Carrie Thompson (NHS)"— Presentation transcript:
Current Issues in Food BSE Claire Appleton and Carrie Thompson (NHS)
Introduction BSE is a form of Transmissible Spongiform Encephalopathy (TSE). It is thought to have first emerged in cattle during the 1970s. The disease is characterised by degenerative brain malfunction. It is referred to by various terms, depending upon the type of mammal that has been infected. –E.g. CJD in humans, BSE in cattle and scrapie in sheep. The actual cause of such diseases is unknown, but thought to be initiated by Prions (proteinaceous infectious particles). The Prion theory is thought to aid the transmission of the disease through species. Under microscopic post mortem of an infected mammal, sponge-like holes in the brain can be observed, hence the name ‘Spongiform.
Introduction Continued ….. The Food Standards Agency (FSA) have released a number of statistics relating to BSE incidence and reported cases in a range of European countries.. Year No. of cases
Introduction Continued …. As the graph illustrates (slide 3), the United Kingdom has many more cases than any other country in Europe. The reasons for this are unknown. Although figures in the UK appear astronomically high they have significantly decreased over the past four years. The tables seem to be on the turn however, in countries such as Spain where the number of cases was 0 in 1999, but rose to 82 in 2001 and even though in 2002 figures have dropped to 10, this is now higher than that in the UK. Sweden on the other hand, has yet to report a case of BSE. This could be due to a number of factors including; –tighter regulations regarding hygiene, cattle conditions, import and export. –more successful eradication programmes.
Summary of Scientific Articles Although many articles were found, four will be be the main focus of discussion in order to highlight the current issues raised with regard to the BSE situation. The first article analysed will be that of Weissmann and Aguzzi (1997) which makes suggestions between BSE and the human form CJD. Issues raised in this journal article include; –age of CJD onset in humans –the transmission of the Prion from cattle to humans –sporadic and new variant CJD Weissmann and Aguzzi suggested that the optimum age of CJD onset would be below 35 years. The reasoning for this was not stated.
Summary of Scientific Articles In regards to the transmission of Prions from cattle to humans, it is thought to have originated from cattle that had been fed Prion infected bone and meat meal. However the original source is unclear, but is suspected to have come from scrapie infected sheep. Controversy surrounds such suspicions following experiments where scrapie-infected sheep brain was injected into cattle, which failed to promote a BSE-like disease. The article outlines and highlights the differences between sporadic and new variant forms of CJD. Stating that the Prion banding is different in each case resulting in a variety of symptoms, depending on the type of CJD contracted. If a person is suffering from the sporadic form they emit symptoms such as rapid progressive dementia, cerebellar dysfunction and muscle jerk. However a person with new variant CJD expresses symptoms such as behavioural changes and late stage intellectual deterioration.
Summary of Scientific Articles Several lines of evidence argue for a causal relationship between BSE and vCJD. This can be supported by the high prevalence of vCJD in countries where BSE incidence is subsequently high. For example, in Great Britain the number of cases of vCJD follows the same incidence pattern as BSE, therefore it is debatable as to whether or not this is a coincidence. The second article reviewed, Kerr and Venter (2001), concentrates predominantly on the issue of humans consuming and contracting sheep derived BSE. The article suggests that, –“BSE-infected sheep could pose a greater human health risk than infected cattle.” Contradictions are then made in this article stating that other sources have assumed that BSE cannot be contracted naturally through sheep.
Summary of Scientific Articles The third article addressed found in the Trends in Neurosciences journal, attempts to clarify the origin of BSE. It states that it is likely to have emerged from the UK. It is thought that BSE is caused by feeding cattle contaminated meat and bone meal (MBM), as mentioned on previous slide. Yet, this was fed to all cattle in Europe and the USA since the 1950s. So why is it that the UK seems to be blamed for the problem? Evidence suggests that young calves are responsible for this outbreak, as they are more susceptible to developing BSE. In the 1970s, only British calves were fed MBM, and not other counties. This is the only piece of evidence to suggest that BSE is UK derived.
Summary of Scientific Articles The final article by Ferguson-Smith, M. A., (2001) reflected on the issue of how much or little the general public were informed about the BSE issue and what more could have been done. They claim that the public were not informed about the possibility of sheep being infected with Scrapie and that the risk assessment had changed. Ferguson-Smith implied that the reason BSE was “an exclusively British disease” is still unknown. Stating that procedures followed in Britain were also followed abroad and so that could not be the problem. To conclude Ferguson-Smith suggests that BSE is likely to have originated from Southern England in the 1970s, but still it is unknown why and how.
Summary of Issues Raised The articles have attempted to highlight controversial and uncertain issues surrounding BSE and CJD. The main issues raised in the literature obtained include; –the transmission of BSE from sheep to cattle to humans, –the prevalence and incidence of BSE in Europe, –reasons why the UK have had the most reported cases of BSE, –sporadic and new variant CJD, –transmission of the disease by Prions. Although there have been many suggestions into to how VSE came about and how it is transmitted across species barriers, there has been little assurance of knowledge. Many of the statements made in the literature found, are just suggestions and there are no definite explanations.
Summary of Issues Raised It is clear that more extensive research is required into TSEs, namely BSE and CJD, in order to prevent such an outbreak re-occurring. In comparison to the media interpretation of the BSE sargor, the scientific literature has provided a less biased insight into the current BSE issue. It attempts to educate the reader by logical explanations and scientific reasoning behind the unanswered questions that remain surrounding the BSE issue.
Conclusions It seems evident that the transmission of BSE to humans is by Prions, which causes CJD. BSE originated from contaminated MBM. BSE has the highest incidence rate in the UK. CJD can target all groups of people, even vegetarians? The threat of sheep derived BSE producing an outbreak a big as BSE from cattle seems unlikely.
References Ferguson-Smith, M. A., (2001), “The reaction to the emergence of BSE in the UK:what was done and what perhaps might have been done better”, Biologies, 325, 25-26 Food Standards Agency, (2002), “BSE incidence- reported confirmed cases”, www.document, http://www.bsereview.org.uk/data/eumap/incidence_table.htm Kerr, C., Venter, C., (2002), “BSE infected sheep?”, Trends in Microbiology, 9, No. 9 Weissmann, C., Aguzzi, A., (1997), “Bovine Spongiform Encephalopathy, an early onset variant CJD”, Current Opinions in Microbiology, 7, 695-700