As some may know, I come from a farming background. I grew up on a beef farm and my grandparents owned a large international animal (primarily dairy cows) exporting company. I am old enough to remember the first appearance of Mad Cow in the UK in the late eighties. In fact, I did a research project at university on BSE after the first case was identified in Canada in 1992 and yes, I did the project the same year it arrived..... I know firsthand the devastation such diseases can have on a family's livelihood and a country's economics.
Case in point, in 2003, the announcement of a single case of mad cow disease undermined the entire Canadian cattle industry. The discovery of a single case of BSE on May 20th, 2003 immediately slammed the door on export markets for Canadian beef and cattle. The result, according to Statistics Canada, was a loss of $2.5 billion in exports, causing a loss of $1 billion in labour earnings, and the loss of 75,000 jobs. In 2003, Canada was the 3rd largest exporter of beef on a global basis owning 15% of the market. As of 2013, Canada was 6th at 4.6%. The industry has never fully recovered. So it was with much dismay I learned that a case of Mad Cow had been found in Alberta, the first case since 2011.
Bovine Spongiform Encephalopathy (BSE) or Mad Cow disease as we prefer to call it, is a transmissible spongiform encephalopathy, or TSE, that attacks the central nervous system of cattle. Other types of TSE include scrapie in sheep, chronic wasting disease (CWD) in deer, and Creutzfeldt-Jakob disease (CJD) in human beings. The cause appears to be associated with a protein called a prion, which is naturally present in people and animals. Diseases caused by prions are known as spongiform diseases, because the brain tissue in infected individuals is filled with holes, giving it a sponge-like appearance. Although prions are found throughout the brain, the symptoms of spongiform diseases vary according to the regions they are most concentrated in. There are currently no effective treatments and no vaccines for spongiform diseases. All are fatal.
Ever since Stanley Prusiner coined the term prion in 1982 and showed that purified prions can transmit spongiform disease, skeptics have been trying to prove him wrong. The idea that a protein can self-replicate goes against everything we know about transmissible diseases. Even the simplest viruses contain genetic material, DNA or RNA,that codes for proteins necessary for function and transmission.
Prions cannot be destroyed by boiling, alcohol, acid, standard autoclaving methods, or radiation. In fact, infected brains that have been sitting in formaldehyde for decades can still transmit spongiform disease. Cooking your burger 'til it's well done won't destroy the prions! Unlike bacteria or viruses which are killed or inactivated via disinfection or cooking, when it comes to prions you can't kill what isn't alive!
From a safety perspective, at least in Canada feeding animals other animal protein bi-products such as offal (aka brains, spinal cords etc) has been banned as a way to limit introduction of TSE infected materials into the food stream. In 1992, 37,380 cases of BSE were identified in the United Kingdom reaching its peak with almost 800 new cases a week. With changes in feed programs and banning cows >30 months to be used for human consumption the cases of BSE in the UK dropped to 1,144 by 2002. In Canada it was 10 years between our first and second case and 4 years since our last case. TSE's are a fact of life and have been dating back to the early 1700's, but they are now sporadic in nature and have never stopped me from enjoying a perfectly BBQ'd T-bone!