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Officials on both sides of the U.S.-Canadian border are
saying that the discovery of BSE in a 6-year-old Alberta
animal "is not unexpected," but rather consistent with projections
that additional Canadian cases would be uncovered as a result
of "residual infectivity" following the ruminant-to-ruminant
feed ban Canada implemented in 1997.
"We've seen the same thing in other countries," Dr. Brian
Evans, Canada's chief veterinary officer, told Meatingplace.com
. The United Kingdom implemented its first feed
ban in 1988, but it wasn't until 1992 or 1993 that it broke
the back of the BSE epidemic and began to see infections
fall off."
"We simply have to look at the BSE experience worldwide,"
agreed American Meat Institute Foundation President James
H. Hodges, also speaking to Meatingplace.com.
"Most countries that had BSE also had it after bans were
put in place."
Feed residue may be culprit
Evans explained that because even small amounts of infective
tissue — even as small as a grain of sand — can transmit
BSE when animals are at their most susceptible age, it's
not unreasonable to assume that animals can contract the
disease from residue remaining on a feed bin or feed auger.
He also said "the potential [for infection] will always
be there" as long as other potential vectors of infectivity,
including poultry litter in cattle feed, exist. "That's
why we continue to perform surveillance," he said.
Hodges said ongoing surveillance in Canada and the United
States indicates "a high level of statistical confidence
that if BSE exists in either country, it exists at very,
very low levels."
The geographic location and age of the animal identified
Monday are consistent with the three domestic cases previously
detected through Canada's surveillance program. Evans said
the fact that the age of the infected animal, born in April
2000, is consistent with the bottom threshold of the other
three infected animals discovered — 70 months to 80 months
— is reason for optimism. He cited the Harvard Risk Assessment
for BSE, which indicates that once BSE is significantly
reduced in cattle populations, the disease eventually dies
out. "That said, I wouldn't want to identify a date threshold,
because it would be based upon assumptions that may or may
not happen," said Evans.
Evans said that when Canada uncovers a case of BSE, a molecular
assessment of the diseased tissue is performed to determine
whether the case has a common affiliation with other cases.
He also indicated that a live animal test for the disease,
if it becomes available, would help in further eradicating
the disease.
Industry reaction muted
Meanwhile, Agriculture Secretary Mike Johanns indicated
he anticipated no change in the status of beef or live cattle
imports to the United States from Canada.
Elsewhere, Stan Eby, president of the Canadian Cattlemen's
Association, said Monday's diagnosis "is proof that [Canada's
surveillance program] is working."
AMI President J. Patrick Boyle said, "Canadian government
data demonstrate a high level of compliance with feed restrictions
aimed at preventing the transmission of BSE via feed." |
