Mad
Cow Disease is the
common name for a
degenerative
neurological disease of
cattle called Bovine
Spongiform
Encephalopathy (BSE).
BSE is one example of a
class of neurological
diseases called
Transmissible Spongiform
Encephalopathies (TSE).
The disease has become a
household word around
the world largely due to
an outbreak of the
disease in the United
Kingdom involving over
183,000 confirmed cases
[1].
While the transmission
means for the disease is
still not well
understood, it is
proposed that the
outbreak may have
originated from feeding
the cattle meat and bone
meal that was derived
from sheep that were
infected with scrapie, a
TSE commonly found in
sheep and goats. The
spread of the disease
was probably accelerated
by feeding meat and bone
meal from infected
cattle back to young
calves.
While BSE is exclusively
a disease of cattle, the
outbreak in the United
Kingdom coincided with
over 150 human cases of
a rare brain disorder
called Variant
Creutzfeld-Jakob Disease
(VCJD). While the
transmission mechanism
is still being debated,
the U.S. Center for
Disease Control has
indicated that the
persons who contracted
VCJD in the United
Kingdom were infected
through consumption of
cattle products from
cattle infected with BSE
[2].
Variant Creutzfeld-Jakob
Disease is a separate
disease from classic
Creutzfeld-Jakob
Disease. The classic
disease apparently
develops spontaneously
and primarily affects
older patients with a
median age at death of
68 years. The median age
at death for the
patients with VCJD in
the United Kingdom is 28
years [2].
TSE diseases are found
in many species
including BSE in cattle,
scrapie in sheep and
goats, transmissible
mink encephalopathy in
mink, feline spongiform
encephalopathy in cats,
chronic wasting disease
(CWD) in deer and elk
and kuru, classic CJD,
Gerstmann-Straussler-Scheinker
syndrome, fatal familial
insomnia, and VCJD in
humans.
The agent that causes
BSE is thought to be a
prion, which is an
abnormal form of a
common protein that has
the ability to reproduce
itself. The agent is
only found in brain
tissue, the spinal cord,
and in the retina of the
eye, and it is only
found in these locations
in cattle over 24 months
of age (with rare
exceptions).
Since 1989, the Animal
and Plant Health
Inspection Service
(APHIS) has prohibited
the importation of live
cattle and cattle
products, including
rendered protein
products, from countries
where BSE is known to
exist. In 1997, these
restrictions were
extended to include all
of the countries in
Europe. On December 7,
2000, APHIS extended the
ban to include all
imports of rendered
animal protein
products, regardles of
species. This was due to
concern about potential
cross-contamination of
feed.
In 1997, the FDA
prohibited the use of
mammalian protein in
animal feeds given to
cattle and other
ruminants.
The discovery of BSE
infected cows in Canada
in 2002 and in the U.S.
in 2003 may cause
additional restrictions
to be placed on the use
of animal byproducts in
animal feed. If grease
from rendered animal
carcasses is banned from
feed, biodiesel
production might become
the best opportunity for
disposing of this
important product of the
animal rendering
industry.
___________________________
References:
1.
http://www.cdc.gov/ncidod/diseases/cjd/bse_cjd_qa.htm
2.
http://www.cdc.gov/ncidod/diseases/cjd/cjd_fact_sheet.htm
Websites for additional
information:
www.aphis.usda.gov/oa/bse
www.fas.usda.gov/dlp/BSE/bse.html
www.BSEinfo.org
www.afia.org
www.fda.gov/cvm/index/bse/bsetoc.html
www.cdc.gov/ncidod/diseases/cjd/cjd.htm
www.animalprotein.org