The Canadian Food Inspection Agency (CFIA) has concluded its investigation into two cases of bovine spongiform encephalopathy (BSE) that were confirmed in Canada in January 2005, with no additional cases found.
The first confirmation came January 2, 2005, in an eight-year-old Holstein cow that was euthanized and sampled after being identified as a downer cow. No part of the cow entered the human food or animal feed chains and was later incinerated at CFIA’s Animal Diseases Research Institute in Lethbridge, Alberta.
Born on October 5, 1996, the animal left its farm of origin by sale through a livestock auction in June 1999 and was subsequently purchased from a livestock dealer in March 2000, prior to arriving on the index farm. Before its death, the animal had been sick for some time and had experienced posterior paralysis for a few days before a veterinarian was called. It previously had problems delivering its last calf in 2004.
The investigation revealed that the cow had two calves during the previous two years, one born in 2003 and the other in 2004. Both calves were determined to have died of causes unrelated to BSE. An investigation was also undertaken to locate the birth cohorts of the affected animal.
The size of the birth cohort was determined to be 135 animals. The trace-out investigation identified nine living birth cohorts that were subsequently euthanized, sampled, and tested negative for BSE. These animals were disposed of through incineration and did not enter the human food or the animal feed chains. Because birth cohort cattle would presently be seven to nine years old, most had previously died or been slaughtered. Finding more than one case of BSE in a birth cohort is rare. This has been consistently shown internationally, even in the United Kingdom during the height of that country’s BSE epidemic. It has also been demonstrated in all investigations completed to date in North America. The remaining 126 animals were traced as follows:
• five animals had died of causes unrelated to BSE on the farm of origin;
• 110 had died elsewhere or had been slaughtered;
• six animals were confirmed to have been exported to the United States for slaughter;
• four animals were untraceable because of missing records;
• one animal had previously entered Canada’s BSE surveillance program in November 2004 and tested negative for BSE.
A full on-farm investigation into feed purchases and feeding practices was undertaken at the farm of origin, revealing that the index animal was exposed to a dairy ration containing meat and bone meal between early April and mid-May 1997. The animal was further exposed to meat and bone meal in the latter part of September 1997 through a heifer ration manufactured in March 1997. Fifteen percent of the meat and bone meal used in both feed rations was derived from ruminant material, which was permitted under the regulations then in effect.
The investigation revealed that this animal was most likely exposed to a low level of BSE infectivity through consumption of feed containing ruminant meat and bone meal during its first year of life. The suspect lots of feed were manufactured at a time when the use of ruminant meat and bone meal in cattle rations was still legal, before the use of such materials was prohibited in 1997. Given the direct relationship between level of exposure and length of incubation period, the age of this animal confirms that the amount of BSE infectivity present in the feed consumed in 1997 was most likely very small.
The second case was confirmed on January 11, 2005, in a Charolais beef cow that was just under seven years old at the time of death, having been born on March 21, 1998. The animal remained on the farm of birth during its entire life. The cow had separated from the herd, experienced loss of condition, and eventually hind-limb dysfunction that the owner attributed to injury. A private veterinary practitioner was consulted and the animal was euthanized and sampled for BSE testing. Again, no part of the animal entered the human food or feed chain and was subsequently incinerated.
The investigation revealed that the animal had two offspring born within the previous two years, one of which had been slaughtered. The other one was euthanized and incinerated at the CFIA Lethbridge laboratory. The animal was not tested for BSE because it was less than one year of age.
The birth cohort was determined to comprise 349 animals. The trace-out investigation of the birth cohort located 41 live animals that were subsequently euthanized, sampled, and tested negative for BSE. These animals were disposed of by incineration. Because birth cohort cattle would presently be five- to seven-years-old, most had previously been slaughtered or had died of natural causes. The other 308 animals were traced as follows:
• 273 animals were confirmed to be dead or slaughtered in Canada;
• 32 animals had died on the farm of origin;
• three animals were deemed untraceable because of inadequate records.
A thorough investigation into feed purchases and practices, manufacturing processes, and documentation was undertaken at the farm of origin, feed manufacturers, and retailers.
The investigation revealed that the index animal was exposed to four commercial feed sources (calf ration, creep feed, and two mineral supplements) during its early development that may have been the source of infection. Although these four feed sources should not have contained ruminant meat and bone meal, the possibility that one or more of them may have been contaminated cannot be ruled out.
The feed manufacturers were handling ruminant meat and bone meal for the manufacture of non-ruminant feeds during the timeframe of interest. These feed sources were likely manufactured a short time after the feed ban was implemented; however, as historical production records were not available, manufacturing dates could not be confirmed.
Canada’s Feed Ban Effective
After recent independent reviews by CFIA and the U.S. Department of Agriculture (USDA), both agencies determined that Canada’s feed ban is limiting the spread of BSE. Canada’s ruminant-to-ruminant feed ban was put in place in mid-1997, around the same time the United States implemented a similar feed ban.
CFIA’s assessment concluded that the ban was “appropriately designed – incorporating the best science of the day – and implemented.” The review also found compliance with the feed ban’s requirements at rendering facilities and feed mills was high. On average, 95 percent of the country’s feed mills and 93 percent of renderers inspected over the past three years were either fully compliant or reported only minor non-compliance issues, such as documentation requirements, which do not necessarily signify increased risks of cross-contamination of ruminant feeds with prohibited material.
USDA assembled a team of technical experts that arrived in Canada in late January to gather all relevant information for an in-depth assessment on that country’s feed ban and feed ban inspection program. The inspection team’s report states that “Canada has a robust inspection program, that overall compliance with the feed ban is good, and that the feed ban is reducing the risk of transmission of BSE in the Canadian cattle population.”
April 2005 Render