Up until a few months ago, experts assured us that Mad Cow disease would never rear its ugly head in North America. In May, however, researchers found that an eight-year-old cow in Alberta, Canada, had indeed succumbed to bovine spongiform encephalopathy. Officials admitted with embarrassment that, although the cow had died in January, the brain was not tested until four months later because the cause of death pointed to pneumonia and that made it a low priority. Happily, the animal did not make it into the human food chain since the abattoir deemed it a “Downer” or 4-D (dead, dying, diseased, disabled) cow. Instead, she went to a rendering plant where her diseased remains appeared to end up in low-quality commercial dry dog food.
According to a spokesperson at the Food Inspection Agency, the pet food manufacturer, Champion Pet Foods, “voluntarily recalled the pet food in the U.S. in conjunction with FDA (Food and Drug Administration) standards” and also pulled the kibble, produced for four different brand names in late February to mid-March) from the shelves in Canada. Government spokespeople on both sides of the border were quick to point out that canines do not contract the disease so their people need not worry. (Cats, on the other hand, can contract a feline version of the disease and U.K. vets have attributed more than 100 deaths to feline spongiform encephalopathy, with many more suspected).
In the meantime, borders were closed to Canadian beef and almost 2,000 Albertan cattle met the same fate as the hundreds of thousands slaughtered in the U.K. in the 1990s. Though none of the other cows tested positive, it’s impossible to determine the health status of cows from the suspect herds who were previously slaughtered. Five bulls, for instance, who officials connected to the diseased cow, were purchased by a rancher in Montana and subsequently slaughtered without the benefit of testing. None seems to know what happened to the carcasses. Did they end up in pet food too? The story raises a number of questions and gives us a new reason to be mindful of the quality of diet we feed our animals.
First recognized in sheep as scrapie, transmissible spongiform encephalopathies (TSEs) are now thought to be caused by abnormal proteins called prions. The infectious proteins, which cannot be destroyed by heat, sterilization, or irradiation, transform normal proteins to a similar abnormal state and eventually lead to lesions in the brain. TSEs are 100% fatal.
In the relatively short time they’ve had to study TSEs, scientists have determined that the disease is species-specific and does not cross what experts call the “species barrier”. In other words, we know that elk suffer and die from the TSE called Chronic Wasting Disease, but so far humans have not contracted the disease. Scientists conclude then that humans are resistant to this TSE. Humans are not, however, immune to Mad Cow. Doctors in the U.K. continue to diagnose people with a new variant of Mad Cow, Creutzfeldt-Jacob disease, a condition linked directly to eating BSE-positive beef. With an incubation period of up to forty years, we’ll no doubt be seeing more diagnoses in the future. While cows, mink, sheep, cats, elk, mule deer, hamsters, and some zoo animals including a lion, tigers, pumas, a bison, and eland have died from species-specific versions of the spongiform diseases, other animals seem immune. For example, to date, no pigs, chickens, horses, or dogs appear to contract TSEs. Because of this, some scientists, factory farmers, and the government reason that “Downer” cows – the ones most likely to carry Mad Cow — can still be fed as a protein source to pigs and chickens. Vice versa, while, since 1997, the law has prohibited feeding cows to cows, farmers and feedlots can happily dish up their bovines a serving of pigs and chickens.
However, at least one study indicates science may not be that simple.
Since the animal had changed hands several times and given birth to a handful of offspring, it made the officials’ job challenging. Thankfully, the farmer’s herd tested negative. In the meantime, however, borders shut down and experts pondered how the animal contracted BSE and what are the ramifications of this disease to our animal companions?
First, we need to consider what causes the disease.
The disease, first recognized as scrapie in sheep, has existed for hundreds of years. But only in the 1980s did scientists in the U.K. discover that Mad Cow disease could jump from one species to another. Cattle, who for years had been fed high protein animal feed consisting of sheep and other animal parts, started showing signs of BSE. Cats in the U.K. contracted the disease (to date the U.K. reports 100 confirmed cases but vets suspect there are far more) and zoo animals, including a lion, bison, cheetahs, tigers, and eland died from BSE as well. In North America, reports of elk wasting disease and a similar disease in deer continue to come in. Most frightening of all, humans have developed a new variant Creutzfeldt-Jakob Disease (CJD), a disease linked specifically to eating contaminated beef.
To prevent the tragedy suffered in Europe, both American and Canadian governments changed animal feed policies in 1997 to halt the practice of feeding ruminants to ruminants
- Since 1990, BSE has been a reportable disease in Canada. This means that any suspected case must be reported to a federal veterinarian.
- We have a ruminant-to-ruminant feeding ban. This means that Canada does not allow the rendered carcasses of ruminants – such as sheep, goats, cattle, deer, and elk – and mink to be fed to ruminants. This eliminates the major transmission vector of BSE and other diseases.
- Canada also has the Canadian Cattle Identification Program for cattle and bison, making it possible to trace individual animal movements from the herd of origin to slaughter.
- Canada’s BSE surveillance system doubles the rate recommended testing rate set by international standards. Since 1993, Canada has tested approximately 10,000 animals.
- The current Canadian BSE import policy restricts animals and animal products from entering Canada from countries that are known to have BSE.
- We have a control and eradication program for both chronic wasting disease and scrapie (other TSEs) in Canada.