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Bovine Spongiform Encephalopathy (BSE) is a progressive,
fatal disease of the nervous system of cattle. It is
what is known as a transmissible spongiform encephalopathy
(TSE). Other TSEs include scrapie in sheep, chronic
wasting disease in deer and elk, and Creutzfeldt-Jakob
disease (CJD) in humans. Although the exact cause of
BSE is unknown, it is associated with the presence of an
abnormal protein called a prion. There is no treatment
or vaccine currently available for the disease.
British scientists have suggested that a newly recognized
form of CJD, known as variant Creutzfeldt-Jakob disease (vCJD),
found in Britain in recent years, may be caused by human
exposure to BSE. People afflicted with this strain of
the disease tend to be from a younger portion of the
population than those with classical CJD. BSE has
gained a high profile as a result.
There have only been two cases of BSE ever diagnosed in
this country. The first case was found in 1993 in a
beef cow that had been imported from Britain in 1987.
The animal carcass and the herd it came from were destroyed
and additional measures were taken immediately by the
federal government to deal with any risk that Canadian
cattle might have been affected. The second case of
BSE was reported May 20, 2003. The animal was
condemned at slaughter so no meat from the carcass entered
the food system. the Canadian Food Inspection Agency (CFIA)
responded with a comprehensive investigation that tested
some 2000 animals. All test results were negative for
BSE. BSE has been a reportable disease in Canada since
1990.
BSE is an unusual disease in that the time between an
animal's exposure to the disease and the on set of clinical
signs ranges from three to six years.
Animals with BSE may show a number of different symptoms
including nervous or aggressive behaviour, abnormal posture,
lack of co-ordination or difficulty rising from a lying
position, decreased milk production, and weight loss despite
an increased appetite. These symptoms may last for a
period of two to six months before the animal dies.
Scientists believe that the spread of this disease in
cattle in Great Britain 20 years ago was caused by feeding
protein products made from infected cattle or sheep.
This occurred in the late 1970s and early 1980s. It
was then magnified by the practice of feeding rendered
material from slaughtered cattle to other cattle. the
protein that is linked to BSE is resistant to normal
inactivation procedures such as heat, which means that it
may not be destroyed in the rendering process and could
remain active in rendered material. in 1988, Great
Britain banned the use of this rendered material in animal
feeds, thus removing the potentially contaminated material
from the food chain. as a result, since the winter of
1992-1993, the number of BSE cases in Great Britain has been
progressively dropping. In addition, other possible
methods of transmission are still being scientifically
investigate.
There is no test do diagnose BSE in live animals,
although a tentative diagnosis may be made based on clinical
signs. Diagnosis can only be confirmed by microscopic
examination of the animal's brain after its death.
Canada, as well as many other countries, has taken
precautions to prevent the introduction and spread of BSE.
These measures include the following:
- the creation of a surveillance program in which the
brains of cattle are tested for the disease.
- since 1997, Canada has banned the feeding of
rendered protein products from ruminant animals (cattle,
sheep, goats, bison, elk or deer) to other ruminants.
- making BSE a reportable disease, such that any case
of BSE must be reported to a federal veterinarian.
- the creation of a Canadian Cattle Identification
Program for cattle and bison, making it possible to
trace individual animal movements from the herd to
origin of slaughter.
- controlling the importation of products that are
assessed to have a high risk of introducing BSE into
Canada. Canada only allows the importation of live
ruminants and their meat and meat products from
countries that Canada considers to be free of BSE.
Canada also has additional import controls for animal
products and by-products from countries that have
confirmed BSE in native animals. Their animal
products are assessed on a case-by-case basis and may be
permitted entry if they are judged not to present a risk
of introducing BSE.
- Canada has not imported ruminant-derived meat and
bone meal for the purpose of livestock feeding from
Europe for more than a decade. In December 2000,
the CFIA suspended the importation of rendered animal
material of any species from any country that Canada did
not recognize as free of BSE.
- Canada requires the removal of certain cattle
tissues, known as specified risk materials, at
slaughter. Specified risk materials are tissues
that, in BSE-infected cattle, contain the agent that may
transmit the disease. In diseased animals, the
infective agent is concentrated in certain tissues such
as the brain and spinal cord.
If you notice an animal is showing any signs of the
symptoms of BSE, contact your veterinarian, or notify the
local CFIA district office, which is listed in the blue
government pages of the phonebook.
Check your feedbags carefully for the label "do not feed
to cattle, sheep, deer or other ruminants." Such feed
contains material prohibited for ruminants.
If you mix feed on your farm, make sure that you do not
mix feeds for non-ruminants (such as horses, swine or
poultry, etc.) with any feed for ruminants.
If you have both ruminants and non-ruminants on your
farm, or if you mix your own feeds on your farm, keep all
invoices for feeds.
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