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From: Terry S. Singeltary Sr. (216-119-132-86.ipset12.wt.net)
Subject: CANADA BSE "We saw such clusters in Britain, and in Switzerland and France."
Date: January 13, 2005 at 1:31 pm PST

Canada discovers its third mad cow

* 18:06 12 January 2005
* NewScientist.com news service
* Debora MacKenzie

Canada has found its third cow infected with BSE - bringing the number of native mad cows detected in North America to four.

All of the infected cows detected so far were born in Alberta, Canada, where a clinical case of BSE was found in an imported British cow in 1993. This raises the question of whether the infection might have been limited to the province by chance, or whether other regions of the continent are just not looking hard enough to find infected cattle. In particular, the US surveillance programme has come under criticism.

The most recently discovered infected cow was born in March 1998 - seven months after feeding beef remains to cattle was banned. The Canadian Food Inspection Agency (CFIA) says it was probably infected by feed made just before the ban.

It was detected as part of Canada's surveillance programme which, like the one in the US, focuses on "high risk" cattle, those found dead or "downers" unable to stand. Experience in Europe has shown that these cattle are much more likely to have BSE than apparently healthy ones.

The programme - which discovered the country's first case in May 2003 - found another Alberta-born mad cow in December 2004, this one born just before the 1997 feed ban. The sole case found so far in the US, in December 2003, was a downer born and probably infected in Alberta.


Infection clusters

"It is possible that certain feed industry habits, perhaps, have caused the infection to cluster in a particular region," says Marcus Doherr of the University of Bern, Switzerland, who helped develop the BSE risk-assessment procedure now used worldwide. "We saw such clusters in Britain, and in Switzerland and France."

"Perhaps it would be worth trying to find out if there is something different in Alberta compared to other parts of North America," say Doherr. US officials plan to send a team to Canada to investigate the case.

But cattle and feed are traded so freely within North America that the BSE risk has been repeatedly assessed by scientists as probably equal in each country. Cattle infected by rendered, imported British cattle in the early 1990s "could have been transported throughout Canada and the US, following normal animal movement patterns", says the CFIA.

If there is no difference in risk levels across North America, it may be possible that Alberta's surveillance programme is better at finding BSE. Canada has tested 24,000 cattle in the past year and found three cases, yet the US has tested nearly 180,000 and found none. The chance of finding a case should depend on the number of cattle tested and not on how large that sample is compared to the national herd, notes Doherr.

The US programme has been criticised because it is voluntary. "We learned in Europe that as long as testing is voluntary and people don't want to find infected cows, then they will try not to," says Doherr. And that can be done, he says, by submitting downers for testing that have other diseases or have simply had accidents, not cows with symptoms that suggest BSE.


http://www.newscientist.com/article.ns?id=dn6875

TSS





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