Post by Claire Brimacombe, University of Birmingham
Bovine spongiform encephalopathy (BSE) or “Mad Cow Disease,” as it is more publicly known is a transmissible neurodegenerative disease affecting cattle. Importantly, it is also transmissible to humans and there is currently no treatment available. Scientists around the globe are working to better understand the infectious agent that causes the condition – a misfolded prion protein (PrPSc). In a new study, published in the Journal of General Virology, scientists used an improved detection technique to detect PrPSc in peripheral tissue from affected cattle. The findings suggest revised guidelines are needed on material banned from meat destined for animal feed or human consumption. This could help efforts to eradicate this disease.
In the late 1980s and early 1990s the UK experienced a major BSE epidemic with approximately 180,900 confirmed cases of BSE between 1989 and 2002. The source of the outbreak is not known but it was able to spread and cause such widespread devastation due to the presence of contaminated meat products in cattle feed. The cost to the UK economy was in excess of four billion. Since banning ruminant meat products in animal feed, the number of confirmed BSE cases decreased such that in 2011 only 6 cases of BSE in the UK were identified compared to 37,000 in 1992. Transmission of BSE to humans results in the human form of the disease, variant Creutzfeldt-JakobDisease (vCJD). 176 cases of definite/probable vCJD have been identified in the UK between January 1990 and September 2012.
PrPSc proteins increase in number in the host by acting as a template for the misfolding of normally folded prion proteins PrPC. This leads to the accumulation of misfolded protein that is unable to be broken down by enzymes in host tissues, causing fatal tissue damage in the brain. The new study uses a relatively new detection technique, protein misfolding cyclic amplification, to investigate the presence of PrPSc in peripheral tissues of cattle infected with BSE. Since its first use in 2001, this technique has been modified and is now capable of detecting trace amounts of infectious prion protein. Historically, misfolded prion proteins have only been detected in neuronal tissues of cattle. This publication supports recent studies that PrPSc is present in extra-neuronal peripheral tissues of BSE-affected cattle. Furthermore it indicates that PrPSc is present in other peripheral tissues to include all tissue along the intestinal tract.
While banning specified risk material (SRM) from animal and human consumption has significantly reduced the number of cases of BSE in the UK every year, and reduced the risk of transmission to humans, BSE has not been eradicated and thus the risk still remains. The World Health Organization believes it is possible to eradicate BSE by preventing contaminated material entering the food chain. This would be beneficial for human health and also the livelihood of beef farmers in the UK and abroad. Improved PrPSc detection techniques are certainly a step forward and will inform policies and guidelines relating toSRM.