EDMONTON — Canada's food safety watchdog says a small amount of leftover contaminated feed was the most plausible cause of a case of mad cow disease discovered last February on a farm near Edmonton.
The Canadian Food Inspection Agency say no part of the Black Angus beef cow entered the human food or animal feed systems.
The agency says no significant events could be linked to this case of bovine spongiform encephalopathy (BSE).
The February case — the 19th in Canada — prompted a few countries to place temporary restrictions on Canadian beef imports.
A report on the investigation says the Angus cow was born at a nearby farm almost two years after Canada brought in more strict controls on animal feed to prevent BSE.
It says a previous case of B-S-E was diagnosed on the same birth farm from an animal born in 2004.
"No significant events could be linked with this case but the potential for the carry-over of a small amount of residual contaminated feed could not be discounted,'' reads the CFIA report released Monday.
The report says the chances of finding other cattle infected with BSE that were born within one year as the February case "remain extremely low.''
It is "highly improbable'' that the BSE was caused by contamination at either a slaughterhouse or a rendering facility, the report says.
An outbreak of BSE in 2003 cost Canada's cattle industry billions of dollars when countries around the world shut the door to Canadian beef.
BSE is a fatal and untreatable wasting disease of the brain and nervous systems. It is caused by rogue proteins called prions, which can be spread through contaminated feed.
Humans who eat infected beef can develop a fatal disease called variant Creutzfeldt-Jakob disease.
Fewer than 250 human cases have been reported worldwide.
The CFIA report said its investigation found 746 cattle that were either born within one year at the same farm as the BSE cow or had access to the same feed.
Any of these cattle that were found alive were placed under quarantine. Some have been destroyed or will be destroyed under the agency's BSE rules. Others have died, the report says.
More than 300 animals were traced to a slaughter plant or feedlots.
The report says 118 animals were exported for slaughter and the importing country was notified.
The CFIA said its trace-out of the remaining animals is ongoing.
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