What Canadians Need to Know About Mad Cow Disease

Updated July 11, 2001

What Is Mad Cow Disease?

Mad Cow disease, or its scientific name Bovine Spongiform Encephalopathy (BSE), is a fatal brain-wasting disease in cattle which was first identified in the United Kingdom (UK) in 1986.  The disease has an incubation period lasting 4-7 years, but ultimately is fatal for cattle within weeks of its onset.(1)

BSE is one of a number of Transmissible Spongiform Encephalopathies (TSEs) – a family of diseases in humans and animals which are characterized by sponge-like lesions in the brain.  Other examples of TSEs are found in sheep, deer, elk, mink and even the feline species.  In deer and elk, TSE is commonly referred to as “Chronic Wasting Disease” and in sheep the disease is known as “scrapie.”  It is widely believed that cattle in Britain developed BSE as a result of being fed the rendered carcasses of dead sheep that were infected with “scrapie”.

There is a great deal of speculation as to the original cause of BSE.  According to the widely-held “prion theory”, the BSE agent is composed largely, if not entirely, of a self-replicating protein referred to as a “prion.”  Another theory suggests that the agent is virus-like and possesses nucleic acids which carry information.  Strong evidence collected over the past decade supports the prion theory, but the ability of the BSE agent to form multiple strains is more easily explained by a virus-like agent.

Epidemiological studies conducted in the UK suggest it is spread through cattle feed prepared from carcasses of other ruminants – any of a group of even-toed, hoofed, cud-chewing mammals, including cattle, deer, and elk.  No one knows for sure how the first cow (or cows) got BSE, but we know it spread throughout Britain and eventually the world through the cannibalistic practice of making cattle feed out of the bits of cattle (offal) that are not fed to humans.  Like a “chain-letter”, offal from a BSE cow, infected many more cattle and offal of those cattle infected many more.

According to British customs figures, more than 200,000 tons of potentially contaminated feed were exported around the world.(2)  The UK Sunday Times recently reported that Prosper de Mulder, Britain’s largest rendering company, exported potentially contaminated material to Canada.(3,4)  In a recent worldwide alert the UN Food and Agriculture Organization reported that meat and bone meal from Europe was imported by more than 100 countries since 1986, including Canada.(5)  All those countries are at risk, said the report, and added “All countries which have imported cattle or meat and bone meal that originated from Western Europe, during and since the 1980s, can therefore be considered at risk from the disease.”(6)  As of December 2000 approximately 180,000 cases of Mad Cow disease were confirmed in the UK.(7)  Cases of BSE have since been confirmed in cattle in Belgium, Denmark, France, Ireland, Luxembourg, Netherlands, Portugal, Switzerland, Germany, Spain, Italy, Greece and the Czech Republic.(8)  In December 2000, the World Health Organization issued a warning of “Global Exposure to BSE” and urged that “all countries must prohibit the use of ruminant tissues in ruminant feed”;  in other words – stop cannibalistic feeding practices immediately.  Cattle are herbivores – not cannibals.

What Is New Variant Creutzfeldt-Jakob disease (vCJD)?

New variant Creutzfeldt-Jakob disease (vCJD) — or “Human Mad Cow disease” — is also a fatal brain-wasting disease.  Characterized by dementia and loss of motor control, this hideous disease was first identified in the United Kingdom in 1996.  It is widely accepted in the scientific community that the most likely cause of vCJD is from exposure to the BSE agent via “dietary contamination by affected bovine central nervous system tissue”, or in more simple terms, from eating infected meat.(9)  Originally it was believed that BSE could not jump from cattle to humans.  The hypothesis of a link between vCJD and BSE was first raised because of the association of these two in time and place.  Experts quickly observed that the agent responsible for vCJD is consistent with the agent that causes Mad Cow disease in cattle; In other worlds – it was the same disease.(10)  Scientific studies have since confirmed that vCJD and BSE are indeed the same disease.(11)

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