Overview of Canada's BSE Safeguards
This document provides a comprehensive summary of Canada's actions to address bovine spongiform encephalopathy (BSE). It outlines the nature of the disease, the likely means of introduction of BSE into Canada, and the measures that have been implemented since 1990 to limit risks to human and animal health.
These safeguards have limited Canada's exposure to BSE from known affected countries and reduced the potential for the spread of BSE within Canada. As a result, all available information continues to support the determination that the level of BSE in Canada is extremely low and declining. Canada's safeguards also include the removal of potentially harmful cattle tissues from the human food supply. This and other measures within the meat inspection system protect the safety of Canadian beef and beef products from BSE
BSE and vCJD
BSE, also known as "mad cow disease," is a progressive, fatal disease of the central nervous system of cattle. The disease was first confirmed in southern England in December 1986. A rapid rise in the number of cases of BSE in the United Kingdom (U.K.) followed the initial diagnosis, with a yearly peak of 37,280 confirmed cases in 1992.
Although the origin of BSE in cattle remains unconfirmed, the epidemic in the U.K. is believed to have resulted from feeding cattle meat and bone meal (rendered ruminant protein) containing the tissues of BSE-infected animals, beginning in the 1970s. Several factors may have combined to produce the epidemic, including changes to the rendering process in the U.K. and the increased use of meat and bone meal in calf feed in the years preceding the outbreak. The decline of the epidemic is due to the introduction of feed controls. There is no evidence to indicate that BSE is a contagious disease.
Variant Creutzfeldt-Jakob Disease (vCJD), a rare human disease that affects the central nervous system, was first diagnosed in the U.K. in 1996. Scientific evidence indicates that vCJD is caused by the same agent that causes BSE in cattle. This is a significant finding, as before 1996 it was not believed that BSE could be naturally transmitted from cattle to humans. It is widely believed that the human cases of vCJD appearing in the U.K. and Europe are the result of eating cattle tissues infected with the BSE agent. Medical authorities believe that both the Canadian and American vCJD patients contracted the disease during one of multiple extended stays in the U.K. during the 1980s and 1990s.
No cases of vCJD have been linked to eating Canadian beef, and, based on the measures described below, the risk of contracting vCJD in Canada is extremely small.
A Low Level of BSE Enters North America
It is now hypothesized that BSE entered North America during the 1980s when Canada and the United States imported a limited number of cattle from the U.K. Given the long incubation period of BSE, some of these cattle could have been infected with BSE despite appearing healthy when entering either country. Canada imported 182Footnote 1 such animals from 1982-1990. The last shipment of 14 cattle, still in quarantine in 1990 when the import ban was announced, was not released into Canada. Therefore, only 168 animals actually entered the Canadian cattle herd during this period and 1989 was effectively the last year that U.K. cattle imports entered Canada.
One of these cattle, in 1993, tested positive for BSE and was diverted from the food and feed systems. With the exception of 68 animals that had already died or been slaughtered, Canada took the extraordinary action to require that any of these U.K. cattle remaining in Canada had to be returned to the U.K. or euthanized and tested for BSE. All animals tested were negative for the disease. Of the 68 animals, 10 are considered to have posed the greatest risk because they originated from farms in the U.K. that eventually reported cases of BSE after the animals had been exported.
Import Controls Restrict Offshore Exposure
Since the 1980s it had been prohibited to import many of the products that had the potential to spread BSE in Canada. These restrictions had been put in place to protect Canada from other foreign diseases, such as foot and mouth disease. While not directed at BSE, these measures reduced the probability of BSE entry into Canada.
In 1990, based on the dramatic increase of BSE in the U.K., Canada banned the importation of cattle from the United Kingdom and Republic of Ireland. A monitoring system was also initiated for the remaining U.K. animals in Canada that had been imported since 1982. In 1991, beef products from European countries not free of BSE were also officially banned. Over the following years, Canada continued to bolster its BSE safeguards, expanding the regions from which animals, certain feeds and ruminant products were restricted. The United States also introduced similar import measures. However, the movement of animals and animal products between Canada and the United States continued.
Although current information would suggest that a low level of BSE had already entered North America prior to 1990, the measures taken since that time effectively restricted the subsequent entry of further BSE into Canada and the United States. Because of the shared BSE risk and the high level of integration of Canadian and American cattle industries, both countries have continued to take consistent measures to jointly manage the risks of this disease in North America.
Controls Limit BSE Spread
It is now considered probable that one or a few potentially infected animals imported into Canada before 1990 would have entered the animal feed system. Rendered meat and bone meal from such animals would have been included in cattle feed, which was permitted at the time, and led to the development of additional cases of BSE in Canadian-born cattle. The same scenario would have been equally possible with cattle born in the United States, where similar feed practices were followed.
In 1997, acting on the recommendations of the World Health Organization, Canada and the United States introduced preemptive feed bans. In doing this at that time, the recycling of infectivity within the cattle herd would have been dramatically reduced, the incidence of BSE present in Canada's cattle herd would have crested and, through normal attrition due to slaughter and death, would have begun to decline.
Canadian and American feed restrictions are virtually identical. Although there are some small differences between the two countries' bans (for example, Canada prohibits the feeding of poultry litter and plate waste to ruminants, whereas the U.S. does not), the overall purpose and design of the feed controls in both countries is consistent. Both Canada and the United States perform regular inspections of industry to verify compliance with their feed ban requirements. Although the possibility of cross-contamination exists within complex animal feed production and distribution systems, experiences in other countries, such as the U.K., have indicated that Canadian and American feed controls would still have limited the spread of BSE and can be expected to lead to the eventual eradication of the disease.
In addition, not all cattle are equally susceptible to developing BSE. Research has shown that the majority of animals become infected early in life, usually within their first year. Most of these young animals, in keeping with normal North American industry practices, would be slaughtered before infective levels of the disease could develop.
Canada on the Watch for BSE
Since 1990, BSE has been a reportable disease in Canada. This means that, by law, all suspected cases of BSE must be reported to the Canadian Food Inspection Agency.
Canada introduced passive surveillance in 1991 when a program to test rabies-negative mature cattle for BSE was initiated. In 1992, Canada began actively monitoring the national cattle herd for animals with clinical signs consistent with BSE. This surveillance program is intended to monitor the level of BSE in the national cattle herd. Over the years, surveillance levels have been regularly enhanced. Since 1993, Canada has consistently met and exceeded its OIE surveillance requirements for all years except 1995 when 90% of the annual target was met.
Canada's surveillance testing targets the highest risk animals for BSE as recommended by the World Organization for Animal Health. Since the beginning of 2003, the small number of BSE cases detected through intensive testing of these high risk populations provides further evidence that the level of BSE in Canada is extremely low. Canada encourages the nation-wide submitting of eligible samples through a reimbursement program for producers and veterinarians, and various awareness and education materials. All animals tested are held pending final results.
The surveillance program also provides an indication of how well measures such as the feed ban and import controls are working. To date, surveillance results indicate that the feed ban is effectively limiting the spread of BSE. If the feed ban had allowed BSE to continue to spread through the animal feed system, the number of animals detected within Canada's targeted surveillance regime would be much higher.
More telling than the number of cases is the older age of the affected animals found in Canada (5-XX years). Research has shown that higher doses of the BSE agent will shorten the incubation period, leading to the development of disease symptoms at an earlier age. The fact that the surveillance program has not detected BSE in younger animals provides further evidence that the feed ban has limited the recycling and prevented amplification of the BSE agent in the feed system.
Slaughter Practices Reduce Food Safety Risks
In Canada, the majority of cattle are slaughtered between 18 and 22 months of age. Considering the long incubation period of BSE, these animals, if infected, would be considerably less likely to develop infective levels of the disease.
Even if infected animals were to survive long enough to develop into full-blown BSE cases, most of these animals would not leave their farms as they would be dead, down or displaying neurological signs. Effective June 29, 2005, for humane reasons it is illegal to load and transport downer cattle in Canada. If some animals displaying neurological signs were presented for slaughter, they would be screened out during pre-slaughter inspection.
Removal of SRM
As outlined above, Canada's BSE safeguards work together to systematically limit the risks associated with BSE. Import restrictions prevent additional infectivity from entering Canada, the feed ban continues to limit BSE spread and decrease the level of the disease present in Canada, and inspection at slaughter removes potentially affected animals from the food system.
After all these safeguards have reduced potential risk, Canada implements an additional measure to maintain food safety. Research has shown that BSE concentrates in certain parts of infected cattle. These tissues, known as specified risk material (SRM), are removed from all cattle slaughtered for human consumption.
This measure is internationally recognized as the most effective way to protect human health from BSE. Removing SRM means that even if an infected animal enters the slaughter system the resulting meat and meat products do not contain those tissues known to contain BSE.
Enhancing the Feed Ban - The Final Safeguard
The CFIA introduced enhancements to the feed ban in July 2007. SRM are now banned from all animal feeds, pet foods and fertilizers. These measures accelerate our progress toward eradicating the disease from the national cattle herd by preventing more than 99% of any potential BSE infectivity from entering the Canadian feed system.
The Canadian Food Inspection Agency expects that it may find a small number of additional cases of BSE as Canada's surveillance program continues to test high-risk cattle from the national herd. However, because of the suite of measures already in place, these cases would not increase risks to food safety or animal health.
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