Canadian official: BSE risk 'low'
Thursday, July 14, 2005
As the chief veterinary officer for the Canadian Food Inspection Agency, Brian Evans doesnít see a great need to develop a live-animal BSE test. He also doesnít believe that every single animal should be tested at slaughter.
Instead, with the number of BSE cases on the downward slide and effective control measures in place, Evans believes the best place to catch any other potential cases is on the farm.
He addressed the hot issue during Illinois Farm Bureauís Canada Market Study Tour stop at Ag Canada in Ottawa.
In terms of testing cattle for BSE, ìitís important to focus on the population at risk.î
And that population is cattle aged 30 months or older that may have been exposed to ruminant feeds. Evans said if contracted, BSE typically infects tissue in cattle between 32 and 38 months of age.
ìThe clinical signs are not the stumbling, falling down cow, however,î he said. ìItís a change of behavior. Itís gradual.î
With such subtle signs early on, Evans believes a well-informed producer can be as good as or better at identifying the disease than can be accomplished by testing every animal for BSE.
ìNobody knows the behavior of the herd better than the producer,î Evans said. ìI place the same value on a farmer identifying one (high-risk animal) as opposed to blindly testing 100,000 animals at slaughter.î
Evans said the risk of BSE now is particularly low because the disease peaked in 2002-03 in North America. He explained that BSE takes about five years to develop in an animal and it must be contracted through ruminant feeding.
A feed ban on specified risk materials was put into place in 1997 and, to date, only five cases have been confirmed in North America. With the source for contracting the disease nearly eliminated in cattle feeding, Evans said the five-year risk period closed in 2002-03.
At its peak in the United Kingdom (UK) in 1992, there were 37,000 cases of BSE ó or about four confirmed cases every hour that year, Evans said.
ìIt was so broadly distributed before it was detected (in the UK about 20 years ago), it took some time to reverse,î Evans said.
But, even at its peak, Evans said BSE has caused about 160 human deaths with the possibility of one or two per year for the next 40 years ó totaling close to 200. By comparison, Evans said early predictions from England estimated that as many as 10 million people would die from BSE around the world.
ìIn terms of risk to human health, itís low,î he said. ìIím not discounting the fact that weíve had deaths from a preventable disease. Itís just not nearly as rampant as predicted.î
Along with the feed ban, Evans said the control measure that removes dead, downer, diseased, and/or dying animals from the system should be the key to nearly wiping out BSE. With the measures in place, he doesnít see a burning need to develop a live-animal test for BSE.
ìWeíve been hearing about new tests for BSE, but Iím not going to get too excited about it,î he said. ìThe disease will be nearly eradicated by the time we have a dependable live-animal test.î
Evans said researching a vaccine for BSE also may yield little benefit, as it is a non-conventional disease.
ìBSE is not an infectious agent. Itís a protein structure in a cell that starts to transform,î he explained. ìSo we canít develop a vaccine because the body canít build an immunity to it.î
To date, Evans said 24 countries have identified indigenous cases of BSE and two countries have identified imported cases since it was first detected in the UK.
Compared to the peak year of cases in 1992 (37,000), Evans said there were 873 BSE cases reported worldwide in 2004 and 211 cases so far in 2005.
He believes there still may be one or two cases found in either Canada or the U.S. But at that point, the animals will have been removed from the food and feed system and incinerated.
ìWhen we find a positive test, itís important to remind people that this animal wasnít infected yesterday,î he said. ìItís a reflection of what took place years ago.î
Looking ahead, Evans said he would rather focus more research and resources on diseases such as foot and mouth, West Nile virus, avian influenza, cancer, and HIV as opposed to BSE ó a disease that affects many fewer people and animals by comparison.
ìBSE is not a disease I want to spend billions of dollars on when thereís other diseases that present a more significant risk to both animals and humans,î Evans said. ìWeíre now investing (in BSE research) based on consequence and not risk.î
Canada may spend $6 billion to $10 billion to manage BSE, which ìin a worst-case scenario may kill six to eight cattle,íí he said. ó Daniel Grant
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