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.
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, worldwide 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.
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].
Greger, Michael. “Mad Cow Disease” March 1996): 9 pp. Internet. 5 April 1996.
St. Rosemary Educational Institution. "Mad cow Disease: History & Causes." http://schoolworkhelper.net/. St. Rosemary Educational Institution, Last Update: 2016. Web. Retrieved on: Friday 20th May 2016. http://schoolworkhelper.net/mad-cow-disease-history-causes/.