The Mysteries Surrounding Creutzfeldt-Jakob Disease
Creutzfeldt-Jakob Disease is a killer. What we know is that it wastes no time. Creutzfeldt-Jakob Disease will kill a person within one year of contraction. It is yet unknown how Creutzfeldt-Jakob Disease chooses its victims, but it does seem to have accomplices, known as the spongiform encephalopathies, in the rest of the animal kingdom. It is possible that it may be known what means Creutzfeldt-Jakob Disease uses in order to annihilate its victims, but the theory surrounding that is still controversial. By examining the facts and observing the evidence we shall one day uncover the truth behind this malicious killer.
Creutzfeldt-Jakob Disease is a rare neuro-degenerative disease. Creutzfeldt-Jakob Disease is a rare neuro-degenerative disease that leads to the loss of coordination, dementia and death. Death usually occurs within a year of the onset of symptoms. Creutzfeldt-Jakob Disease is a human disease and can be dormant for as long as thirty years. The average age of onset is sixty years, but there are recorded instances of onset as easily as sixteen years and as old as 80 years. It is estimated that, world-wide, between 0.5 and 1 case per million population occurs annually. Increased incidence in some regions of the world has been attributed to the possibility of a genetic predisposition. In the United States the incidence has been reported as being 0.9 deaths per million population attributable to Creutzfeldt-Jakob Disease. This is an inexact figure however, due to the fact that Creutzfeldt-Jakob Disease is not a reportable disease in the United States (Holman) and the Center for Disease Control does not actively monitor the disease (Altman). To track the disease the Center for Disease Control has initiated a four-state study of death certificates (Altman), but since death certificates are not always accurate Davanpour) the survey may not provide an accurate assessment. This leaves the true prevalence in the United States and other countries remaining a mystery. Compounding the uncertainty, autopsies are rarely performed on atypical dementia patients (Harrison) because medical professionals fear infection (Altman). The officially reported rate of Creutzfeldt-Jakob Disease incidence is less than one case per million people per year (World). An informal survey of neuropathologists, however, registered a theoretical range of 2 – 21% of all dementia as actually Creutzfeldt-Jakob Disease (Harrison) and hundreds of thousands of Americans suffer from severe dementia every year (Brayne; United). Two other studies average about a 3% Creutzfeldt-Jakob Disease rate among dementia patients (Mahendra; Wade). A preliminary 1989 University of Pennsylvania study showed that 5% of patients diagnosed with dementia were actually dying from Creutzfeldt-Jakob Disease (Boller). It would seem that Creutzfeldt-Jakob Disease is seriously underdiagnosed.
The most common misdiagnosis of Creutzfeldt-Jakob Disease is Alzheimer’s disease (Harrison). Creutzfeldt-Jakob Disease was even described as ?Alzheimer’s in fast forward (Wlalzek).? The symptoms and pathology of both diseases overlap. There can be spongy changes in the brain (a classic effect of Creutzfeldt-Jakob Disease) in Alzheimer’s disease, for example, and senile plaques deposited on the brain (a classic effect of Alzheimer’s disease) in Creutzfeldt-Jakob Disease (Brown). The causes may overlap as well; epidemiological evidence suggests that people eating meat more than four times a week for a prolonged period have a three times higher chance of suffering dementia than long-time vegetarians (Giem), although this result may be confounded by vascular factors (Van Duijn). Paul Brown, medical director for the U.S. Public Health Service (Gruzen), said that the brains of the young people who died from the new variant Creutzfeldt-Jakob disease in Britain even look like the brains of Alzheimer’s patients (Hager). Stanley Prusiner, the scientist who coined the term prion, speculates that Alzheimer’s may in fact turn out to be a prion disease as well (Prusiner). In younger victims the disease could look like multiple sclerosis or a severe viral infection, according to Alzheimer’s expert Gareth Roberts (Brain). Twenty percent or more of people clinically diagnosed with Alzheimer’s disease are found at autopsy to not have had Alzheimer’s at all (McKhann). At Yale, out of 46 patients clinically diagnosed with Alzheimer’s, 6 were proven to have actually had Creutzfeldt-Jakob Disease at autopsy (Manuelidis). In another post-mortem study 3 out of 12 Alzheimer patients actually died from a spongiform encephalopathy which is the class of diseases that Creutzfeldt-Jakob Disease belongs to (Teixeira). These spongiform encephalopathies appear to be diseases that enter the brain and cause holes to appear which can then alter an animal’s functioning and abilities. Eventually death occurs and the brains of these animals strongly resemble sponges.
At one point the causative agent was thought to be slow viruses of the central nervous system, but no viruses were ever found and people afflicted with spongiform encephalopathies never exhibited signs of inflammation, indicating that the immune system was not involved in these diseases (Quinion). Recently Professor Stanley Prusiner received the Nobel Prize for his theory that Creutzfeldt-Jakob Disease and other spongiform encephalopathy diseases were caused by proteinaceous infectious particles, or prions. Prions are proteins without DNA that occur in the brains of all mammals and are harmless until an altered form adopts the role of an infectious agent (Altman). The normal function of prion proteins is not completely understood, but recent research on mice that lack the gene which encodes the prion protein suggest that it protects the brain against dementia and other degenerative problems associated with old age (Gee).
Sometimes rogue prions are produced by genetic mutations. This explains why some cases of Creutzfeldt-Jakob Disease in humans appear to be inherited. If these rogue prions are transmitted from an infected animal to a new host they will convert any normal prions that they encounter into copies of themselves (Gee). The end result produces a brain full of vacuoles, especially in the cortex and cerebellum, and covered in amyloid plaques (Altman). Prusiner’s theory is still controversial as it has yet to be demonstrated experimentally. However, it is of great importance because it is now established that a type of Creutzfeldt-Jakob Disease called new-variant Creutzfeldt-Jakob Disease, has, on occasion, been passed to humans through the consumption of beef from cattle infected with Bovine Spongiform Encephalopathy, also commonly known as Mad Cow’s Disease (Quinion). It is believed that the cattle themselves were infected through farmers feeding them with protein from sheep infected with scrapie, another spongiform encephalopathy (Quinion) suggesting that these diseases can jump across species barriers.
Due to the fact that prions can be found in the brains of all mammals it is probable that most mammalian species develop these spongiform encephalopathies. Specific examples include Scrapie, the spongiform encephalopathy of sheep, TME (transmissible mink encephalopathy) which affects mink, CWD (chronic wasting disease) which affects muledeer and elk, and most commonly known is BSE (bovine spongiform encephalopathy or mad cow disease). Creutzfeldt-Jakob Disease is not the only known human spongiform encephalopathy. Also known to affect humans are GSS (Gertmann-Straussler-Scheinker syndrome), FFI (Fatal Familial Insomnia), Kuru, and Alpers Syndrome. The human diseases are characterized by loss of motor control, dementia, paralysis wasting, and eventually death usually following pneumonia. GSS occurs at approximately 2% of the rate of Creutzfeldt-Jakob Disease (Chesebro). It usually occurs in the fourth or fifth generation, and was once thought to be familial or genetic, but has been found to be sporadic as well. GSS is characterized by cerebellar ataxia and motor problems. Dementia is less common than with Creutzfeldt-Jakob Disease and the course of the disease lasts several years until death occurs, whereas Creutzfeldt-Jakob Disease patients seldom live more than a year. FFI pathology is characterized by severe selective atrophy of the thalamus and presents an untreatable insomnia. The pathogeneses of FFI are largely unknown. Alpers Syndrome is the name given to the prion disease in infants. Kuru is the condition that first brought prion diseases to prominence in the 1950’s.
Kuru was found in geographically isolated tribe in the Fore highlands of New Guinea. The route of transmission was established to be through the ingestion of brain tissue of dead relatives for religious reasons, especially by pregnant women of the tribe. They ground the brain tissue into a pale gray soup, heated it and ate it. Clinically, the disease resembles Creutzfeldt-Jakob Disease. Other tribes in the vicinity with the same religious habits did not develop the disease. It is speculated that at some point in the past a tribe member developed Creutzfeldt-Jakob Disease, and as brain tissue is highly infectious this allowed the disease to spread. Afflicted tribes were encouraged not to ingest brain tissue and the incidence of disease rapidly declined and is now almost unknown (Chesebro).
Scrapie was the first example of spongiform encephalopathy to be noticed and has been known about for many hundreds of years. The two most likely methods of transmission of scrapie in sheep are infection of the pasture with placental tissue carrying the agent followed by ingestion making it an acquired infection. It is also believed to be infectious through a genetic disorder, which has led many people to speculate that careful breeding could eliminate the disease, however, to date, this has never been attempted (Chesebro). More well known, in light of current events is Bovine spongiform encephalopathy also known as Mad Cow Disease. An outbreak of Bovine spongiform encephalopathy occurred in Britain in the late 1980’s and is believed to have been brought on by a food supplement given to cows in the United Kingdom that included meat and bone meal from dead sheep (Hager). The transmissibility across species between sheep and cows has led many people to fear that ingesting the beef from infected cows could lead to an outbreak of Creutzfeldt-Jakob Disease among humans. There have been no cases of Creutzfeldt-Jakob Disease reported that can be concretely linked to the ingestion of infected beef. However, on March 20, 1996 the Spongiform Encephalopathy Advisory Committee (SEAC) of Great Britain announced that 10 cases of a previously unrecognized form of Creutzfeldt-Jakob Disease had been identified and may be linked to the Bovine spongiform encephalopathy epizootic in Great Britain, where more than 155,000 cattle were affected from 1986 through 1995. SEAC expressed ?great concern? about the identification of these cases; it is possible that they might represent the beginning of an outbreak of new variant Creutzfeldt-Jakob Disease in humans that would parallel the course of the epizootic of Bovine spongiform encephalopathy in cattle in the United Kingdom, but with a delay of 5 to 10 years. In addition, if new variant Creutzfeldt-Jakob Disease is associated with Bovine spongiform encephalopathy, there is the possibility that cattle-to-human transmission of disease has occurred in other countries where Bovine spongiform encephalopathy exists (CDC). The committee emphasized that current evidence is insufficient to establish a direct link between Bovine spongiform encephalopathy and new variant Creutzfeldt-Jakob Disease; however, such an association offers the most likely explanation for the occurrence of this cluster of new variant Creutzfeldt-Jakob Disease cases.
The major evidence for the existence of new variant Creutzfeldt-Jakob Disease is the recognition of a new neuropathologic profile and the unusually young ages of the United Kingdom patients. In addition, the clinical course of the disease was atypical of classic Creutzfeldt-Jakob Disease. All ten cases