The Canadian Food Inspection Agency (CFIA) confirmed on July 4th that a mature beef cow from Manitoba suffered from 'mad cow disease,' making it Canada's sixth case of the disease in recent years. But the agency says there's no reason to panic.
Dr. George Luterbach, a Senior Veterinarian with CFIA, says it's fairly uncommon that more than one animal on a farm will become infected.
"It's not like infectious disease that spreads easily," he says.
"Other factors also come into play such as genetic resistance" and the fact that not all animals eat the same feed on the same farm or in the same proportions.
BSE is widely thought to be transmitted through feed containing minced cattle remains, particularly brain and spinal tissue. Canada banned this type of feed in 1997, but any cow born prior to the ban may still have consumed bad feed. The animal in this case was over 15-years-old.
Luterbach also points out that it was caught because Canada's inspection regime is "second to none in the world."
The Manitoba cow is Canada's sixth home-grown case in three years of the fatal disease known scientifically as bovine spongiform encephalopathy (BSE), so called because it turns an animal's brain tissue spongy. As in all five previous cases, none of the cow's meat entered the food chain.
Unravelling the Risk of BSE
Marc Richard, spokesperson for CFIA, says that cows are most susceptible to acquiring BSE from eating infected feed during their first year of life. This means, the disease must have incubated for at least 14 years, which is considerably longer than the average.
"Typically the incubation period is in six to seven year range, but there are other experiences around the world that show incubation periods that are much longer," says Luterbach.
In fact, there is still a lot about BSE that is unknown, such as what affects the length of this incubation period or if the theory of 'nuggets' of contaminated feed is enough to explain the diseases pattern of infection.
An infected mother can also pass the disease to her offspring which is another reason why we may still see new cases even so many years after cleaning up contaminants in the feed.
In order to catch any cases related to this one, the CFIA has begun attempting to locate the cow's birth farm, herd-mates, and the origins of the feed they may shared. They are also looking for a calf she bore in 2004.
Human Health Concerns
The real concern of BSE is its human toll. If infected meat enters the food supply, it could lead to its human variant called Creutzfeldt-Jakob (vCJD) disease, a nerve disease which is always fatal.
Worldwide there have been 190 cases of vCJD, 85 percent of which occurred in Britain stemming from their massive mad cow outbreak in 1986. That epidemic affected 180,000 animals from roughly 35,000 herds and millions more were culled before it was finally contained. There has been one human case in Canada but the victim had been a resident of England during the epidemic so it is believed it was contracted there.
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