The latest case of bovine spongiform encephalopathy (BSE) surfaced in a six-year-old dairy cow in the Fraser Valley on the Pacific coast during a national surveillance programme.
But Canadian officials said on Sunday that beef for human consumption remained safe because the BSE-infected parts of cattle do not enter the food chain.
"This finding does not affect the safety of Canadian beef. Tissues in which BSE is known to concentrate in infected animals are removed from all cattle slaughtered in Canada for domestic and international human consumption.
"No part of this animal entered the human food or animal feed systems," said health authorities.
It was the fifth case of mad cow detected in Canada since 2003 and the second this year.
The cases provoked US and Japanese embargoes on imports of Canadian cows and beef, costing Canada's cattle farmers $6 billion before they were lifted last year.
The infected cow was discovered
in British Columbia
Canadian authorities said they would conduct a thorough investigation into the source of the new infection, which comes after controls were tightened on cattle feed, to which earlier cases were sourced.
Since the discovery of Canada's first BSE case in 2003, about 100,000 animals have been tested in a surveillance programme, which targets the animals most at risk from the affliction.
Mad cow disease has been connected to the fatal brain-wasting disease in humans called variant Creutzfeldt-Jakob disease.