Essay/Term paper: Mad cow disease

Essay, term paper, research paper:  Science Reports

Mad Cow Disease


Bovine spongiform encephalopathy (BSE), better know as Mad cow disease is a
relatively new disease. Most sources state that BSE first showed up in Great
Britain in 1986 [Dealler p.5] but some say it popped up in 1985 [Greger p.1].
However the official notification was not until 21 June, 1988 [Dealler stats.
p.1]. Spongiform encephalopathies are invariable fatal neurodegenerative
diseases and there is no treatment nor is there a cure for this disease [Greger
p.1]. The recent scare of BSE has arisen because of the contraction of
Creutzfeldt-Jakob disease (CJD: see Appendix B) in humans from eating beef
products. Although there are many forms of Spongiform encephalopathies that
affect a wide range of animals, BSE has received the most attention because
many people in the world consume beef and people are that they might contract
the disease from eating a burger at their favourite fast-food restaurant. In
this essay I will discuss BSE and other forms of Spongiform encephalopathies,
how it affects the ani mal, what causes the animals to contract the disease, and
the recent issues of BSE in the world. I hope to set out the true facts about
BSE and that it only affects a small percent of the world population. Due to
the fact BSE is a new disease most of my information might be proven wrong in
the future because there is a great deal of testing going on in the scientific
community. They are also very concerned about this new disease and the effects
it can have on humans if it is not stopped.
Bovine spongiform encephalopathy is not some bacteria and it is not a virus,
but in fact it is an infectious protein or prion [Greger p.2]. Before I go into
more detail, I would like to discuss what a prion is. A prion is composed solely
of proteins, and lacks genetic material in the form of nucleic acids. They are
the tiniest infectious agents known, they can only be viewed under the strongest
of electron microscopes [see appendix A]. Most scientists are puzzled because
nucleic acid is the basis reproductive material needed in all other life forms
[Britannica vol.9 p. 978]. Because of their unique makeup, prions are
practically invulnerable. They can survive for years in the soil. Chemical
disinfectants, weak acids, DNAase, RNAase, proteinases [Dealler p.8],
ultraviolet light, ionising radiation, heat, formaldehyde sterilization, and
chemicals that react with DNA [Greger p.2], all have little effect on the
infectivity of the prion. Only marinating your hamburger in Drain-O would make
your burger safe to eat [Greger p.2].
BSE, is a slowly progressing degenerative disease affecting the central
nervous system of cattle. BSE is the same as most of the other spongiform
encephalopathies, they evoke no immune response and consequently slowly
accumulate for an incubation period up to 30 years. You cannot detect them,
purify then, nor can you isolate them [Greger p.2]. One of the main issues that
affect most farmers is how do they know if a cow has BSE. Cattle affected by BSE
develop a progressive degeneration of the nervous system. Affected animals may
display changes in temperament, such as nervousness or aggression, abnormal
posture; incoordination and difficulty in rising, decreased milk production, or
loss of body condition despite continued appetite [Kent p.10]. However it has
been noted the signs in American cows is much different. They instead stagger to
their death like downer cows do. "A downer cow" is referring to the industry
term which describes cows who fall down and are too sick to get up [Greger p.4].
There is no treatment so all affected cattle die. The incubation period ranges
from two to eight years [Hodgson p.2]. Following the onset of clinical signs,
the animal's condition deteriorates until it dies or is destroyed. This usually
takes from two weeks to six months. Most cases in Great Britain have occurred in
dairy cows between three and five years of age [Dealler Bio p.7]. The parts of
the cow that is affected by BSE are the brain, spinal cord, and retina from
naturally infected animals have been found to be infective and also the lower
ileum (intestine) from experimental cattle inoculated was found to be infective
[Varner p.3].
Great Britain is the site where the major problem of BSE started. The
increase of BSE in the UK was mostly due to the fact that farmers were feeding
their cattle a bovine food which included parts of dead sheep that had scrapie
[see Appendix B.]and also the offal [see Appendix B] of dead cows that carry the
BSE disease. This method of preparing the bovine food started in 1980, in order
to be protein concentrated which in return made the cows increase their milk
yield. Most people did not know BSE could be transmitted through the food
derived from dead sheep and cattle. Because the normal incubation period for a
cow is 2-8 years, most of the BSE infected cattle did not start to show signs
until sixth and seventh year. Due to the fact that a very small amount of the
cows that were infected with BSE showed the symptoms early in the 1980's , they
were not detected as having BSE. Most of these cows were then recycled into
bovine food, which was then feed to more cattle and more cattle became infected.
It was not until July of 1988 that the feed manufacturers were issued a warning
to stop the production of bovine food with the presence of cattle offal that
were infected with BSE [Dealler pg.2]. And it was not until 25 September, 1990
that bovine offal were specified to be banned from the food of all species
[Dealler stats. p.1].
In 1987 the British Government stated that BSE could not be transmitted
to any other species because it was the same as scrapie [Greger p.1]. They were
proven wrong and within a few weeks a cat died of a hitherto unknown feline
spongiform encephalopathy contracted from an infected cat food. This caused an
all out worry in Britain, fearing that BSE would spread into the human
population. Nursing homes, hospitals, and more than 2000 schools stopped serving
beef or restricted its consumption to a minimum [Greger p.1]. With this the
price of poultry shot up 12 percent and beef prices drooped 10-25 percent
[Greger pg.1] devastating the cattle industry. The number of cases started to
rise, in 1990 it was 300 cases per week and by 1993 it was up to 800 cases per
week [Dealler bio pp. 2-3]. It was in 1993 that the greatest number of BSE cases
were reported in Great Britain with 36,533 (see Appendix A). It has been stated
that 1.8 million infected cattle will have been eaten before the year 2001 and
that is if there are no cases after 1991[ Patterson p.265]. Since there in not
enough information on how BSE can transfer from one cow to another the number of
infectious cattle eaten by the year 2001 might be as high as eight million[Kent
p.10]. If the ban on affected cattle food was applied one year eaearlier,he
number of affected cattle would have been less than half of the number of cows
that are now affected[Dealler issues p.4].
It was in 1994 that one of the biggest scares came when a 16 year old
girl from North Wales claimed to be dying from CJD, which was contracted from
eating a BSE infected beef product. In 1995 a farmer died and another farmer was
dying from CJD. Both of these farmers came from farms that had BSE affected
herds on them[Dealler bio p.4]. The question that puzzles scientists is the fact
that the people that have been affected with BSE are all under the age of 40.
This is so puzzling because the average age that people generally contract CJD
is 57 years old [Dealler p.3]. Up to this date there has been no scientific
proof to prove that BSE can cause CJD in humans, but there is lots of
circumstantial evidence that points to BSE as the cause of the new form of CJD
that is infecting people in Britain[Varner p.4].
The latest outbreak has made the British Government issue an order that
all cows born before 1994 will have to be killed (about six million cows) and
burned[Cox ]. With Great Britain having more than 98% of the cases, world wide
you can see that they have the biggest worry. Canada has only experienced one
case of BSE. The cow was imported from Great Britain in 1987 and was not
diagnosed with BSE until six years later. The Canadian government took
extraordinary measures to deal with the risk of BSE. The measures included the
destruction of the entire herd containing the BSE infected cows and the trace
back and elimination of all other cattle imported to Canada from Great Britain
since 1982. Also, they incinerated all of the carcasses of the dead cattle .
Although I learnt a great deal about BSE while completing this essay,
the facts today may not be true tomorrow. BSE is such a new disease no on knows
for sure what the future will bring. Some scientists even feel this may be a
catastrophic disease. Dr. Richard Lacey a microbiologist from England was quoted
as saying "BSE is much more serious than AIDS"[Greger p.1], meaning there could
be millions of people infected before the transmission of the disease is stopped.
We can only hope the research and drastic measures being t aken will stop this
disease before many more humans and cattle die..


Appendix B

Scrapie- It is a naturally occurring disease of sheep found in many parts of the
world, but not everywhere. It has been known for more than 200 years, and
thought to of started in Spain. Sheep inoculated with scrapie infected tissue
will have a short incubation period, possibly as low as two months. Scrapie can
not be transmitted to humans [Deller pg.1-2].

Creutzfelt-Jakob Disease(CJD)- It was first described in 1920 when it was known
as "spastic pseudosclerosis' or "subacute spongiform encephalopathy'. The
illnesss exists throughout the world and has an annual incidence of
approximately one case per million of the population [Dealer pg.2]. The average
age in a typical CJD in 56 years, and only seven cases between 18 and 29 years
old have been reported. The symptoms start with changes in sleeping and eating
patters and progress over a few weeks to a clearly neurological syndrome. The
disease progresses with deterioration in cerebral and cerebellar function to a
condition which most neurological activity is decreased, sensory and visual
function decays, and the patient dies, possibly after a decrease in lower motors
neurological function and seizures [Dealler pg.3].

Offal-is any of various nonmuscular parts of the carcasses of beef or veal,
mutton and lamb, and pork, which are either consumed directly as food or used in
the production of other foods. Beef offal includes the stomachs, tripe, or large
stomach, brain, heart, liver, tongue, and kidneys [Britannica vol.8 p.881].

Works Cited

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Dealler, Steve. "Biology of BSE"(April 1996): 10 pp. Internet. 5 April 1996.
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Dealler, Steve. "BSE statistics"(April 1996):12pp. Internet. 10 May 1996.
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Dealler, Steve. "History of BSE" (April 1996):4 pp. Internet. 5 April 1996.
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