Presentation on theme: "Sly Richards. The first cases of transmissible spongiform encephalopathies were reported in Great Britain in the 1700’s. The first case was documented."— Presentation transcript:
The first cases of transmissible spongiform encephalopathies were reported in Great Britain in the 1700’s. The first case was documented in sheep and is called Scrapie. In the 1970’s, the prion disease was widely recognized in Papua New Guinea and was called Kuru.
A prion is an infectious agent in the form of a misfolded protein. Prions are different compared to other infectious agents. They have no genetic material and they are smaller than viruses. They are not alive. Prions are responsible for neurodegenerative spongiform encephalopathies. 10% of prion diseases are hereditary and the other 90% are contracted or sporadic. Prion disease is contracted by consuming contaminated meat. All prion diseases are neurodegenerative and lethal. All prion diseases have an incubation period but it can range from weeks to years depending on the spread rate of the prions.
In every organism, there is a protein in the body that scientists believe prions originate from. This protein can misfold and become a prion. When a prion enters a healthy organism, it travels to the brain where the preexisting prion proteins reside and when it touches one of them, that protein becomes a prion, and a chain reaction occurs.
There are three different ways that a species can contract prions: acquired, inherited, or sporadic. The primary transmission method in animals is acquired by ingestion. When an animal dies of a prion disease, other animals can eat it or prions can linger on particles of dirt. If it is in a nearby water source it could contaminate that. Infection can occur from manure and since manure can be near reservoir areas it can leak into the water supply and contaminate it. Prions can also bind to airborne particles and travel large distances.
Sterilization of prions is extremely difficult because of their extremely stable structure. Prions are resistant to all normal methods of sterilization. Effective sterilization relies upon protein hydrolysis, reduction, or destruction of the protein tertiary structure. Bleach, caustic soda, or strong acidic detergents can be used to destroy prions.
PrP c is a normal protein found throughout the body. PrP sc is the infectious form of the protein When it touches the normal protein, the normal protein transforms into the infectious protein which starts a chain reaction. A group of prions starts forming which causes the neuro-degeneration and eventual death.
The name scrapie come from one of the symptoms of the disease. Animals will compulsively scrape against anything they can find which causes rashes and bare spots on the fleece. Other symptoms are excessive smacking of lips, strange walking patterns, and convulsive collapsing.
When a prion infects cattle, it will cause a change in behavior, uncoordinated movements, trouble standing and walking, weight loss despite an appetite, and decreased milk production. Eventually the cow dies. In Europe, there used to be a program called MBM which stood for meat and bone meal. European farmers used to feed cattle the ground up remains of other cattle some of those would be infected and that was how an epizootic occurred.
TME is a rare disease that affects only adult mink and usually only occurs in ranch-raised mink. The symptoms of this disease are behavioral changes, loss of cleanliness, aimless circling, weight loss, matted fur, hind quarter ataxia, and seizures rarely occur.
This causes cervids (the deer family) to slowly lose weight and eventually die. The symptoms include decreased interactions with other animals, listlessness, lowering of the head, blank facial expression, repetitive walking in set patterns, and a smell like rotten flesh.
This disease effects the brains and liver of cats. It symptoms include behavioral changes and ataxia.
This affects exotic zoo animals. This prion infectious disease was spread when these animals were fed supplemented meat and bone meal.
Ostrich can contract this disease, but once they contract it, it has been theorized that the disease is not transmissible.
This form of prion disease affects humans. Symptoms Dementia followed by memory loss, personality changes, hallucinations, speech impairment, jerky movements, balance and coordination dysfunction, changes in gait, rigid posture, and seizures.