Backgrounder: The History of Bovine Spongiform Encephalopathy (BSE)
Fatal
degenerative disease of the brain and nervous system in cattle, where
cells die leaving a brain with a sponge-like appearance.
The
causative agent of this disease is believed to be a prion, an
infectious protean molecule lacking a nucleus that is extremely
difficult to destroy using conventional methods of treatment.
Symptoms of the disease include confusion, poor coordination and belligerence in the afflicted animal.
There
is no current diagnosis for BSE in live animals besides noting clinical
symptoms. The only method of confirmation is to perform a biopsy on
brain tissue
BSE is one of a group of Transmissible
Spongiform Encephalopathies (TSE); others include Scrapie in sheep,
Chronic Wasting Disease in elk and deer and Creutzfeldt-Jakob disease
an inherited disease found in humans.
BSE was linked
to variant Creutzfeldt-Jakob disease (vCJD) a new form the disease
during the early 1990s when the incidence of the disease doubled, and
started occurring in people with no genetic predisposition to it.
BSE
is transmitted to other cattle when protein (especially brain and
spinal cord) or bone from an infected cow is rendered and added to
cattle feed. It generally takes 4 years of incubation before the
disease symptoms occur; during this time the animal is capable of
transmitting the disease. When people eat processed meat from these
infected cattle they can be infected with vCJD.
The
disease was recognized in 1984 in England, unfortunately not before the
UK had shipped BSE tainted cattle feed all over the world.
Since
then, 200,000 cattle have been killed due to BSE; the majority have
been in Britain (over 160,000) other countries include France, Germany,
Italy, Switzerland, Ireland, Canada, Portugal and Denmark.
Canada’s
previous incidence of BSE occurred in 1993 with a single case of a beef
cow imported from England. It died while still on the farm and never
entered the food chain. Both the carcass and the herd where it had come
from were destroyed.
In the current instance of BSE
in Canada, the Canadian Food Inspection Agency (CFIA) believes that the
cow contracted the disease after eating contaminated feed several years
ago.
It wasn’t until 1997 that Canada banned the
practice of feeding ruminants (animals with two stomachs such as cows,
goats, sheep and deer) protein from other ruminants.
Currently,
over 2700 cattle that potentially came into contact with the infected
cow, her offspring or shared feed have been destroyed and tested in
Canada. There have been no other incidences of disease.
The
infected cow was considered to be sick at the time of slaughter and her
carcass was condemned. As such it was determined to be unfit for human
consumption and sent for rendering.
Rendered protein
from this cow was turned into poultry and dog food. (It is still common
practice to feed protein from ruminants to hogs, poultry and pets)
A
voluntary recall of the Champion Pet Food dog food was initiated to
prevent discarded dog food from mixing with ruminant feed.
There is no evidence that dogs can acquire BSE, nor that handling the food can transmit the disease.
