It has been three years since the first domestic case of BSE was identified in a cow in Alberta. Although the immediate crisis has passed, the event serves as a critical example of how countries must adapt to emerging global risks and to low probability/high consequence events in the future. In January 2006, a group of experts was assembled from across Canada to discuss BSE as a case study. They reflected on what did happen in 2003, and identified critical issues that need to be looked at if the country is to be better prepared for similar events in the future. A set of recommendations weret formulated for enhancing risk assessment, communication and science.
Bovine spongiform encephalopathy (BSE), or mad cow disease, was first characterized in cattle in the United Kingdom (UK) in 1986. The disease is one of a family of progressive and fatal neural diseases known as transmissible spongiform encephalopathies, or TSEs. They are characterized by irreversible destruction of brain tissue. Most are believed to be caused by a prion, an infectious agent comprised of a misfolded form of a protein normally present in neural tissue. The primary means of transmission is believed to occur through the use of animal feed containing protein derived from infected animals.
Since the recognition of the disease, an extraordinary saga has unfolded. As of the beginning of 2006, there have been over one hundred and eighty-four thousand confirmed cases in the UK, by far the majority of the close to one hundred and ninety thousand confirmed in twenty-five countries worldwide. Of public health concern has been the unfortunate reality of 166 known human deaths due to consumption of beef from infected animals, with 93 percent of these in the UK. The cause of death is described as variant Creutzfeld Jacob Disease, or vCJD, a fatal brain wasting disorder.
The Canadian cattle industry, an export dependent sector, was dramatically jolted in May 2003 when the initial domestic case of mad cow was identified in a Saskatchewan born cow residing in Alberta. This resulted in a closing of export markets for Canadian beef, live cattle and other ruminant species, and since that time has been estimated to have cost the industry more than $7 billion. Measures introduced both proactively prior to 2003 and in response to the confirmation of BSE resulted in international borders being partially re-opened. The Canadian government has provided $2 billion in assistance programs to the cattle industry for transformative changes and market diversification, and has instituted the removal of specified risk materials from all animals slaughtered in Canada for human consumption as well as an enhanced surveillance program to assess the overall effectiveness of the suite of measures in place.
The Canadian government has proposed amendments to the ruminant to ruminant feed ban introduced in late 1997 that would prohibit the use of specified risk material (SRM) and deadstock in animal feeds.1 Based on the collective international experience, such an approach is recognized as the most effective means to reduce the risk of cross-contamination of feed and to accelerate BSE eradication. The design, implementation and enforcement of the 1997 feed ban were reviewed after two more cases of BSE were confirmed in 2005 and determined by American, Canadian and other international technical missions to be effective. No products from the infected animals detected in 2005 and 2006 entered either the human or animal food systems. However, the most probable cause of all five Canadian BSE cases reported thus far, including the three animals born after the introduction of the 1997 feed measures, remains contaminated feed.
1 Skull, brain, trigeminal ganglia (nerves attached to the brain), spinal cord and dorsal root ganglia (nerves attached to the spinal cord) of cattle aged 30 months or older and the distal ileum (part of the small intestine) of cattle of all ages.