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The confirmation of a case of BSE in Canada is particularly worrying not only in a North American context but internationally. While BSE has spread far and wide from Britain, prior movements have always been explainable and in most cases predicable. Canada, however, seems to have taken all reasonable precautions to protect itself. And the circumstances surrounding this first indigenous Canadian case raise the possibility that it might have been spontaneous. (720 words)

Bovine spongiform encephalopathy (BSE), commonly known as mad cow disease, was first recognized as a disease in Britain in 1985 and the dominant if not only source of infection was identified as being through the feeding of infected meat and bone meal the following year. The use of meat and bone meal in ruminant rations was immediately banned. But as BSE takes more than three years to develop after infection and the disease was in at least its second generation when it was recognized, the number of incidents of the disease naturally continued to increase.

The British press and media had difficulty in appreciating this reality, and preferred to conclude government incompetence. This created widespread and unnecessary concern and mistrust by the public. It was compounded by an inappropriately worded press release by a government advisory committee that was investigating a new variant of Creutzfeldt-Jakob disease (vCJD), a rare but fatal human disease. It suggested that"in the absence of any credible alternative," there was a link between BSE and vCJD.

In the minds of an already sceptical British public, this was a warning that beef was not safe to eat. And nothing from an immediate retraction of the comment to the removal of all beef more than 30 months of age from the food system seems to have had much effect in restoring confidence. While evidence after more than five years of intensive research is still only circumstantial, and the failure of the incidence of vCJD to reach anything like the epidemic proportions originally anticipated in the UK weakens even this link, perceptions still persist at the retail counter where it counts.

It is this legacy rather than its epidemiology that has made BSE so devastating. It is not a particularly challenging disease to prevent or control. You simply exclude all ruminant meat and bone meal from cattle rations or ensure that any meal and bone meal is from safe sources. Canada does both, banning the use of meat and bone meal from cattle rations and banning its import from all countries but those know not to be at risk of having BSE.

The Canadian case of BSE, therefore, could not have been anticipated. Further, the animal was an eight-year old beef cow in Alberta. This is particularly difficult to explain as it would be most unusual for a ration containing meat and bone meal to be fed to beef cattle in Western Canada. Further, BSE is normally contracted by cattle when young calves and in most cases it develops within five years. If the cow as a calf had indeed picked up BSE from an infected ration, other cattle fed the same ration would surely have shown symptoms by now.

While investigations may yet provide a logical explanation as to how this cow came to be infected, the only other explanations are a mis diagnosis or a spontaneous incident. For the former, the authorities are likely to have been very careful to ensure the diagnosis was accurate, particularly in the context of the very unusual circumstance.

While the latter may be regard in the same context as a virgin birth, the disease did some how evolve in Britain years before 1985 when it was first recognized. There are plenty of theories about how this happened, but very little practical evidence as it is not known where or when it occurred. Research prioities hav also naturally focused on it transmission.

If no logical source of infection is found for this case, those seeking an explanation of the origins of the disease will at least have a possible spontaneous incidence of BSE to test their theories on. Finding a logical explanation for the origin of the disease will also take on extra significance as a second spontaneous case would suggest that control of BSE will require more than the prevention of infection.

May 23, 2003