Prion diseases encompass a group of rare degenerative diseases that affect the brain of human and animals like cattle, goats, cats and deer. Prion diseases are also known as Transmissible Spongiform Encephalopathies (TSEs). Transmissible because the diseases are capable of being transferred from one animal to another, Spongiform because of appearance of sponge like holes in the brain of affected animals and Encephalopathic because they are neurodegenerative diseases of the brain (Will). These groups of diseases are fatal and are characterized by a long incubation period (National Institute of Neurological Disorders and Stroke).
Prion diseases cause brain vacuolation, neuronal apoptosis which eventually leads to accumulation of abnormal prion proteins in the central nervous system. (Will) This leads to varied neurologic symptoms to the affected person or animal. These diseases pose a great concern in respect to human and animal health creating need for increased regulation and monitoring of the diseases (The National Prion Disease Pathology Surveillance Center)
The first recorded case of Prion diseases occurred in Europe in 1732. (Brown)It was not until 1924 when German neurologists, Creutzfeldt and Jacob reported a case of a patient with rapidly progressive neurodegenerative disease. The patient, a woman in early 20’s had progressive dementia, ataxia and tremors. (Belay). Prion diseases were recognized to be transmittable in 1936. (Brown)
The most recognized type of Prion disease in human is Creutzfeldt-Jacob Disease (CJD). Other Prion diseases affecting human are Gerstmann – Straussler – Scheinker (GSS), Fatal Familial Insomnia (FFI) and Kuru. (Brown)Both GSS and FFI are very rare hereditary diseases and are found in very few families in the world. Kuru was discovered from people within a small tribe in Papua New Guinea; the disease has since disappeared. In animal, the most recognized TSE is Scrapie affecting goats and sheep and Bovine Spongiform Encephalopathy (BSE), also referred to as Mad Cow Disease. Chronic Wasting Disease (CWD) is yet another Prion disease affecting deer. (Will)
In Human, Prion disease can occur in three different ways; i.e. through transmission, sporadically and hereditary. Transmission of Prion of disease is very rare although they can be transmitted through contact with infected body fluids, tissues or contaminated medical tools. (US Food and Drug Administration) It is important to note that normal sterilization procedure of medical instruments and tools such as through radiation and boiling does not prevent transmission of Prion diseases.
Casual contact, touching or air cannot transmit Prion diseases. Sporadic Prion diseases may develop when normal prions in a healthy person spontaneously change into an infectious form protein. This affected protein may cause a chain reaction altering the shape of prion in other cell to an abnormal form. With inherited cases, the prion protein gene undergoes mutation causing abnormal shaping of prions. This change in genetic composition may be transmitted to an offspring’s of infected individuals. (Belay)
Creutzfeldt-Jacob Disease (CJD) is a rare type of Prion disease, affecting one in every one million people annually. CJD is believed to be food borne occurring sporadically in human. (US Food and Drug Administration)The disease is reported in equal rations between males and females. Patients have varying symptoms, but common symptoms include Psychiatric problems such as depression, unsteady gait and lack of coordination; this generally results in personality changes. Affected patient may also experience insomnia, involuntary movement, also known as myoclonus, confusion and unusual sensation. (Belay)
These symptom deteriorate very rapidly leading to a stage where patient experience mental impairment and loss of ability to speak or make movement. CJD is always fatal, with four to six months of medical illness, which eventually lead to death. Currently there is no known cure of CJD but treatment is aimed at lessening the symptoms and making the patient comfortable. (Belay). Studies have shown that exposure to blood and consumption of meat and other animal organs like brain, kidney and liver is a possible source of infection to CJD. (Belay)
Gerstmann – Straussler – Scheinker Syndrome (GSS) is a name used to describe a heterogeneous group of degenerative disorder with infrequent myoclonus, familial origin, and numerous amyloid plagues. (Belay) GSS is a variant of CJD, although it is mostly associated with mutation. Most of the clinical symptoms found in patient with GSS are the same as those found in CJD. However, the duration of GSS illness and the age of patient at onset of the disease vary from patient with GSS. (Brown)
The most widespread animal prion disease is Scrapie having inflicted thousands of sheep in countries around the world. (Will). The disease is transmitted to the offspring through the placenta. Studies show that scrapie can not be transmitted to humans, but it can be transmitted to cattle. Chronic Wasting Disease (CWD) is the only Prion disease affecting both domestic and wild animals. CWD is different from Scrapie in that it’s not transmitted from mother to offspring.
Studies have shown that it’s transmitted from infected to vulnerable animals through ingestion of abnormal prions and direct contact. Bovine Spongiform Encephalopathy (BSE) was first detected in United Kingdom in 1986. Since then, it has infected over 180,000 cattle in the UK, Canada and US. BSE is an infectious disease but not contagious because it is not excreted. As such, the disease is not transmitted from cow to cow. (Brown)
Prion diseases, also known as transmissible Spongiform Encephalopathies consists of a group of human and animal brain diseases that are consistently fatal and characterized by long incubation period. Creutzfeldt-Jacob Disease (CJD), Gerstmann – Straussler – Scheinker disease (GSS) and Fatal Familial Insomnia (FFI) are some of the most recognized prion diseases affecting human. In animals, the most recognized prion diseases are Scrapie and Bovine Spongiform Encephalopathy (BSE), commonly known as mad cow diseases.
Common symptoms associated with Prion diseases in human include personality change, depression, lack of coordination, insomnia, unusual sensation and myoclonus. These symptoms deteriorate very fast leading to death as there is no medical treatment of prion diseases. As such, these groups of diseases pose a great concern to human and animal health creating need for increased monitoring and regulation.
Works Cited
Belay, Ermias. “Transmissible Spongiform Encephalopathies in Human.” Annual Health Review (1999): 283-314.
Brown, David R. Neurodegeneration and Prion Disease. New-York: Springer, 2005.
National Institute of Neurological Disorders and Stroke. “Reducing the Burden of Neurological Diseases.” 2008. Prion Diseases. Web.
The National Prion Disease Pathology Surveillance Center. CJD Surveillance. 2008. Web.
US Food and Drug Administration. Prions and Transmissible Spongiform Encephalopathies. 2004. Web.
Will, Hueston. “Transmissible Spongiform Encephalopathies.” Journal of Food Science (2005): 70-87.