CANADA has confirmed its second case of BSE. The affected dairy cow was born in the province of Alberta, just like the only other cases of mad cow disease discovered in North America: one in Canada in 2003 and one in the US in the same year.
Also like the previous cases, the infected cow was born and probably infected before 1997. This was the year when feeding cattle with the remains of other cattle, a practice that spreads BSE, was banned in North America.
The discovery highlights concerns about surveillance for BSE in the US. The infection probably arrived with cattle imported from the UK in the 1980s. Normal patterns of animal and feed movements should have spread it across the continent since then. Yet while in 2004 Canada tested 22,000 high-risk cattle and found one positive, the US tested more than 120,000 and found none.
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BSE testing is voluntary in the US, and consumer activists say that cattle with symptoms that suggest they might have BSE are not being sent for tests. There are also questions about the rapid test the US uses, which has a higher rate of inconclusive results than the test used in Canada.
