According to the CFIA, leftover contaminated feed was the most likely source for a case of BSE found on an Alberta farm earlier this year. A report released Monday says the cow in this particular case, which is the 19th in Canada, came from the same birth farm as a previous case of BSE, but no other sick animals have been found — and chief veterinary officer Harpreet Kochhar says no science shows BSE is transmitted from mother to calf.

"No significant event could be definitively linked to this case, however, the carry over of a small amount of residual contaminated feed on the same birth farm is the most probably the most plausible explanation for BSE case number 19," he says

The CFIA report says this makes case 19 unique, as Canada has not previously identified more than one BSE case born on the same farm. The Black Angus beef cow in case 19 was also born two years after enhanced feed ban was implemented. However, since it's been eight years since the ban was enhanced, Kocchar says it's not likely that residual feed is still an issue.

The CFIA has identified 746 cattle that were born on the same farm during the same year as case 19, with over 130 of these animals quarantined, and another 300 traced to domestic slaughter plants.

"We actually tracked down all of the equivalent risk animals," Kochhar says, "either they have been quarantined and they will be put down, or the ones which have actually been sold out, we have traced them back and looked at their histories and if there were any symptoms and we haven't found any of these equivalent risk animals with symptoms that exhibit the same kind of aspects as the BSE case."

The infected cow in this case was disposed of properly, and no part of the animal entered the human food or animal feed systems. Kochhar says Canada's system of surveilling and monitoring BSE is superb, and despite this one case, is working well to keep animals safe and healthy.

"The government of Canada is committed to protecting human and animal health," he says, "and our beef and beef products are really safe in that regard."