|MadSci Network: General Biology|
The research is still relatively young in regards to prion related diseases. It was only recently that enough evidence was collected to build a strong case indicating that the infective agent is only a protein. The mode of transmission which has caused the BSE (bovine spongiform encephalopathy) epidemic in Britain was most likely through feed which contained bone meal and meat from dead sheep. It is believed that the sheep were infected with the disease scrapies (the equivalent to BSE in sheep). The processing methods for making the sheep supplemented feed had changed in the late 1970's. It is believed that the new processing method did not destroy the scrapie causing agent.
There are many question which still remain regarding this type of disease. Modes of transmission would be one of them. The more you know about the mechanism of the disease the more hypothesis about transmission can be reached. For example the infectious agent acts on the brain therefore the brain, and maybe the spinal cord are areas of high concentration of the prions. The cows most likely contracted the infectious agent from eating the sheep's brains. This was an incident where the infectious agent could cross a species barrier (ie infect an organism which is not it's regular host). However, researchers have found that in most cases this is difficult to do.
I suggest reading the article, The Prion Disease by S. Prusiner in Scientific American (January, 1995), and references within. It is a good article which will provide you with the biology of the disease and help you make some educated guesses on its potential modes of transmission.
Hope this helps.
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