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Prion Disease By: Harnoor Hundal Period: 6 Date: 2/25/11
Report:
The Prion Disease
The Prion disease is a deadly group of progressive conditions that are found in animals and humans, and affect the nervous system. In humans, the diseases cause impairment in brain function and memory loss plus more. The signs and symptoms of these conditions typically begin in adulthood, and these disorders lead to death within a few months to several years.
The Prion disease was discovered in 1960s after radiation biologist Tikvah Alper and the mathematician John Stanley Griffith hypothesized that some transmissible spongiform encephalopathies are caused by an infectious agent consisting solely of proteins. In other words, deformed proteins called prions interfere with other brain proteins and end up clogging and destroying brain cells. [10] Diseased prions are usually found in the brain, spinal cord, retina, and other inffected tissues in the body of an animal of human. Prion protein changes are seemingly found mostly in mammalian brains, which also tend to prompt other prions to change their shape. [11] Prions, short for proteinaceous infectious particles or misfolded proteins, are unconventional pathogens composed of infectious protein particles and are resistant to conventional sterilization procedures, and they are resistant to heat, ultraviolet light, disinfectants that are used to kill bacteria and viruses, and radiation. It was always thought that prion disease could only be spread through contact or from mutations, but from recent studies it has been proven that the disease can also be spread through the air. Which brings us to think that every precaution taken to prevent it should be double checked, and made more effecient. The disease consists of a large group of different types of conditions including Creutzfeldt–Jakob disease and Gerstmann-Strãussler-Scheinker in humans, Fatal Familial Insomnia (FFI), bovine spongiform encephalopathyin cattle which is also known as 'mad-cow' disease, scrapies in sheep, and chronic wasting disease in mule deer and elk. [1] Cases can occur in any gender and age, but usually seen in the average age of 62.
There is another form of the prion disease called "kuru" that was found among native peoples of New Guinea who practiced cannibalism as a ritual. The first stage for this disease is called the ambulant stage, and it includes the unsteadiness of stance, gait, voice, hands, and eyes. The second stage, also known as the sedentary stage, is when the patient can no longer walk with some sort of support, severe cases of tremor and ataxia, outbursts of laughter, shock-like musle jerks, and depression. The third stage is the terminal stage, which is when the patient has difficulty swallowing, slurred speech, urination problems, worse case of ataxia, and more. Death for this disease occurs almost 1 year after symtopms start to appear, however the incubation average was about 12 years, and can also be up to 40 years long. But after the end of such rituals, the disease nearly dissapeared from New Guinea.
Every kind of prion disease ends fatal, also no cure has been found available to patients except symptomatic treatment. [7] But recent work and studies show that polymers of amino acid lysine are able to block the spread of prions by targeting plasminogen. [9] A number of medications have been shown in experiments to be effective at preventing prion slow down. Some of them have been shown to delay the incubation times of animals infected with scrapie, but offourse they have limitations when it comes to curing the entire disease in itself. Vaccines have treated infectious prions in mice, which raises hope of a cure for the human version of the "mad cow disease". It is said to seek medical care when you notice that you experience any signs of memory loss or muscle control. As of November 2006, 3 individuals with mad cow disease had been identified in the United States, and 200 individuals worldwide diagnosed with mad cow disease. About 10 to 15 percent of cases are usually inherited result from gene mutations. Most cases seem to appear sporadically, in someone who has no family history of the disease. Only a small percentage of cases seem to occur through infection, that is caused by contact with infected brain tissue. In the final stage of the 'mad-cow' disease, the patient loses all mental and physical functions, falls into a coma, and eventually ends up dying form the disease. Some physicians do not even consider it as a diagnosis, and believe that they might be mistaking it for diseases such as the alzheimer or huntington's disease. But the also believe, that future technology will help to detect what the prions disease really is.
The first type of condition in prion was found nearly 250 years called scrapies, which initially starts with hyperexcitability, itching, and ataxia, but leads to paralysis then death. Prions eat bits of the brian, and create sponge-like holes, which slowly deteriorate within cattle brain, and eventually affect the whole body. [14] It may take an animal 2 to 8 years to actually show signs of it being infected by the disease. The reason of its name is because of the likeliness of animals to rub against the fences of their pens in order to stand up, showing their cerebellar dysfunction. [6] Prion diseases can be speard through infected meat or infected blood. For example, because all cattle consists of th.e 'mad-cow' disease, humans that eat the infected cattle tissue will eventualy die from brain disease called Creutzfeldt–Jakob disease, also known as the human form of the 'mad-cow' disease, which will most probably develop over the course of many years. [13] This disease was named after the person that discovered, and it usually occurs in older people and the brain tends to change for no reason at all, and happens out of nowhere. The form of this disease that occurs from eating infected meat happens to appear in younger generations for the most part. Within weeks or months you can go from being completely normal to having ataxia, or possibly dementia or myoclonus later during the illness.
The Gerstmann-Strãussler-Scheinker disease is a very rare form of prion, and is inherited and found in very few families all over the world. This disease usually forms around the age of 35 to 55. Also, in the early stages of the disease patients most probably experience ataxia, clumsiness, difficult walking, and unsteadiness. After a few years of having ataxia, it gets worse and develops into dementia. Other symptoms for this disease include dysarthria, nystagmus, spasticity, and also disturbance in vision that may lead to blindness. Even though there is no medical treatment for this disease as well, there it can be identified through genetic testing. Symptoms can appear around the age of 25 years old, but they usually occur when a person is in his or her late 50's. The illness can take place from 3 months to 13 years, and it usually last 5 to 6 years before the patients death. This syndrome was first described by Austrian neurologists Josef Gerstmann, Ernst Sträussler, and Scheinker in 1936.
Fatal familial insomnia is another type of condtion found along prion disease. It is a rare autosomal dominant inherited prion disease of the brain. It is mostly caused by a mutation, but can also appear spontaneously in patients without the inherited mutation in a variant called sporadic fatal insomnia. There has been no found treatment for this disease along with the other disease, and also gene therapy has been found unsuccessful. Some cases have proven that sleeping pills do not help, but only make the condition much worse than it should be.
Another type of conditon called chronic wasting disease is progressive disease that affects deer and elk causing small lesions in the brain, and affect deers and elk that are mostly found in North America. Symptoms of this disease include lack of coordination, seperation from their herd, excessive saliva, depression, unusual behavior, weight loss, paralysis, difficulty in they way they swallow, pneumonia, and also increased thirst or urination. Signs of this disease usually last for a couple months before the animal actually dies. They could be as young as 18 months or as old as 13 years before clinical signs take form. CWD can reduce the growth and size of the deer and elk population in areas where the prevalence is high, which happens to be increasing concern for wildlife managers across all of North America. The disease was limited in some areas, but no it is found almost everywhere in North Marica. Also, cwd has been diagnosed in commercial game farms in several states and provinces.
Researches and scientist are trying to find a simple blood test for prion disease, because the availability of a blood test could provide early diagnoses of human prion diseases and perhaps help find cure and/or determine the extent of prion disease infection. There has been a vaccine called the mucosal prion vaccine that has been tested in mice by the NYU school of medicine. It has been made to slow down brain disease in mice which is significantly similar to the 'mad - cow' disease, and they are hoping that it possibly prevents the disease from ever occuring.
All in all, prion disease is a very deadly and rare disease to be trapped in. There are no treatments for prion-related conditions or diseases, they can easily infect the body of an animal or human because the do not elicit any immune response. Because there is no cure found yet patients and animals cannot be saved, and can only be given treatment that helps them live a little easier and soother life during the disease.
Bibliography:
McKenzie, Debora , Virus in the frame for prion diseases, 2007
Ramachandran Tarakad S, Prion-Related Diseases, 2009
Ramachandran Tarakad S, Prion-Related Diseases, 2009
Ramachandran Tarakad S, Prion-Related Diseases, 2009
ScienceDaily, New Research Focuses on Prion Diseases, 2011
Unknown, Proteins alone cause prion diseases, 2009
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