Jul 1, 2003 (CIDRAP News) – A team of experts who reviewed Canada's response to the recent mad cow disease case in Alberta recommended last week that Canada increase its efforts to ensure that high-risk parts of cattle do not end up in either human food or animal feed.
The four-member team recommended that "specified risk materials" (SRM), such as the brain, spinal cord, eyes, and tonsils, be removed from cattle carcasses destined for use in human food or animal feed. In animals infected with bovine spongiform encephalopathy (BSE), or mad cow disease, the infective prion protein is typically found in these tissues.
Under current quality-control procedures, the spinal cord is removed from all meat intended for human use, according to the Canadian Food Inspection Agency (CFIA). (The spinal cord is also removed from meat in the United States.) In addition, in 1997 both Canada and the United States banned the use of ruminant protein in feed for ruminants (cattle, sheep, goats, and other cud-chewing animals). However, ruminant protein can be fed to pigs and poultry in both countries. Swine and poultry are not susceptible to BSE-like diseases, but protein from swine and poultry can be fed to cattle.
"Implementation of an SRM ban is the most critical and valuable central measure for public health protection and food safety and is fully endorsed by the review team," the team of experts said in its report. "An SRM ban would also reduce the risk of infectivity in animal feed."
"A plan for the safe removal, collection and destruction of the SRM should be immediately developed," the report continues. "Measures to ensure that SRM are not included in human food and animal feed should be implemented, enforced and audited for compliance."
In response to the report, Canadian Agriculture Minister Lyle Vanclief said Jun 27 that the government would introduce a new policy on SRM, but did not offer details. "The SRM policy is being introduced as a precautionary measure to further enhance existing food safety and public health efforts," he said in a statement posted on the CFIA Web site.
The review team recommended several other precautions to prevent BSE, including tighter controls on feed for nonruminant animals, increased testing of cattle, expansion of the cattle identification system to facilitate tracing of animals, and more education of people in agriculture and the food industry. Vanclief said the government agrees with the recommendations but that implementing them will take time.
The review team of four veterinary experts from three countries praised Canada's investigation of the BSE case, in which hundreds of cattle from numerous farms were slaughtered and tested for the disease. No additional cases were found.
"The team is impressed with the comprehensive scope, level of analysis and thoroughness of the investigation to date," the report states. "In a very short time Canadian experts have collected and assessed a level of information that exceeds the investigations done in most other BSE-affected countries."
The report says existing precautions against BSE worked effectively in that the infected cow was kept out of the human food chain. The cow was ill at the time of slaughter and was therefore removed from the meat production system and sent to a rendering plant. Testing of the cow's brain was done in May, four months after slaughter, and showed the presence of BSE.
The review team said the Canadian investigation established epidemiologic evidence supporting the probability that the BSE case "was associated with exposure to infective material through the feeding system at some point early in the life of the animal." The cow's herd could have been given feed containing ruminant meat-and-bone meal (MBM) before that was banned from cattle feed in 1997, the team noted.
Past exposure of other cattle to contaminated feed cannot be ruled out, the report says. "The possibility that products were derived from the positive cow, and the possibility that other infected cattle in the late stages of incubation are present in Canadian herds, lead to the conclusion that the adoption of additional measures to reduce or eliminate future exposure are warranted," the team concluded.
The ban on SRM should include brain, spinal cord, trigeminal ganglia, dorsal root ganglia, terminal ileum, eyes, and tonsils, the report states. "The timely and full national implementation of this measure should be a priority," it says. In addition, sampling and testing programs are needed to ensure that cattle skulls and vertebral columns are excluded from systems that mechanically strip meat from bones (advanced meat recovery systems).
Concerning feed restrictions, the report notes that it is difficult to distinguish cattle-derived MBM from MBM made from other mammals or poultry, and this raises a risk of mixing of the two and feeding of cattle-derived MBM to cattle. Whether this justifies a ban on all mammalian MBM in ruminant feed "has to be evaluated," the report states.
On farms where different kinds of animals are raised, systems are needed to prevent mixing of MBM products derived from ruminants and nonruminants, the report asserts. Because it would be difficult to monitor such systems for compliance, it may be more practicable to ban all mammalian MBM from ruminant feed, the team concluded.
The review team also called for "an increased targeted surveillance program" for BSE. Ideally, all adult fallen stock, dead stock, downer cattle, and cattle showing possible signs of BSE should be tested, the report says.
Vanclief said the CFIA and Health Canada "have accepted the balance of the recommended changes to BSE-related policies" and are "determined to revise these policies as quickly as possible. However, many of these changes are complex and require coordination—even harmonization—with the provinces, the industry, and with the United States and must reflect the integrated North American beef industry." He said the changes will be discussed at a meeting of federal and provincial ministers in late July.
The review team included Ulrich Kihm and D. Heim, both of Switzerland, Will Hueston of the University of Minnesota, and S. MacDiarmid of New Zealand, according to the CFIA.