User:Nature's Mockery/Old Transmissible spongiform encephalopathy

 Contagious sponge-brain diseases  Transmissible spongiform encephalopathies are neurodegenerative brain diseases caused by prions, specifically prion isoforms of the prion protein (confusing, right?) called PrPSc or PrPres. Prions are misfolded versions of a host protein, that are able to convert other proteins into copies of themselves. They are also protease resistant, and extremely neurotoxic. They affect humans and animals alike, and have been shown to cross the species barrier easily. They have extremely long incubation periods; in humans they can be up to 50 years. The name 'spongiform encephalopathy' comes from the fact that they literally rip holes in your brain. Symptoms in humans include dementia, ataxia, depression, paralysis, and always lead to death. There is no cure for TSEs. In the US, there are about 75,000 350 cases per year.

Creutzfeldt-Jakob disease
Creutzfeldt-Jakob disease, also known as subacute spongiform encephalopathy, is a neurodegenerative brain disease that usually occurs in people between the ages of 50 and 65. Its symptoms include ataxia, dementia, speech issues, quadriplegia, and death is certain after 18 months, while most only survive 6. The incubation period is estimated at about 30 years. It has 3 forms, based on the way the person was infected.

Sporadic
Sporadic CJD is just that- CJD without a known cause. This form makes up the majority of cases. Some scientists speculate that sporadic misfoldings are natural, but the faulty proteins are usually broken down. Others think it could be a toxin, and there appears to be significant evidence to show that they can affect protein folding, but none conclusively tying it to TSEs or other prionopathies.

Iatrogenic
Iatrogenic CJD is when the exposure to prions is linked to a medical procedure. This can include tainted blood transfusions, contaminated neurosurgical tools , infected organ transplants , and other medical procedures involving blood or brain matter transmission.

An epidemic of iCJD occurred after taken from cadavers became contaminated with prions. 226 cases of iCJD were linked to the faulty treatment, and the exposed patients also have a higher chance of contracting Alzheimer's disease.

Familial
Familial CJD is when a gene inherited from a parent is faulty, and produces abnormal prions. All familial TSEs are autosomal dominant mutations, meaning only one copy of the mutated gene will cause the disease, and any children the person has will have a 50% chance of carrying the gene. It is estimated that 5-15% of all cases of CJD are familial.

Variant Creutzfeldt-Jakob disease
Variant CJD is a disease directly linked to the consumption of beef contaminated with bovine spongiform encephalopathy. Unlike CJD, it affects younger people, with the median age of onset being 28. The symptoms are almost identical to CJD, but the prion involved is thought to be exactly the same isoform as the BSE-causing prion. Patients affected survive for 18 months, but the disease is still always fatal. However, one infected person survived for over ten years. .

killed 177 people, several cats, and almost a million cows. The cause was infected meat and bone meal. The incineration process failed to destroy the resistant prion protein, and when cows ate the tainted food, they would become infected. Their remains were turned into MBM, causing the disease to spread rapidly.

Fatal familial insomnia
Fatal familial insomnia is a disease that is characterized by the complete inability to sleep. The first signs of the disease are progressive insomnia, which leads to the classic signs of a TSE. Eventually, the victim will not be able to sleep. Sleeping pills will just accelerate the progression of the symptoms, and as the name suggests, the disease is terminal. FFI is usually caused by a malformed gene, but very rarely, it can happen sporadically.

Gerstmann-Sträussler-Scheinker syndrome
Gerstmann-Sträussler-Scheinker syndrome is a familial TSE that occurs in people from the age of 35-50. The symptoms include progressive ataxia, dementia, slurred speech, abnormal eye movements, rigid muscles, deafness, and Parkinsonism (in some cases).

Kuru
Kuru, literally 'shaking disease', is a TSE associated with cannibalism. Symptoms include the classic TSE symptoms, as well as shaking uncontrollably, and bouts of laughing, causing some to call it the 'laughing disease'. The had an epidemic of this disease due to them consuming the bodies of people who died.

Variably-protease sensitive prionopathy
Variably-protease sensitive prionopathy is a disease very similar to sCJD, but stands out due to all tests for CJD showing nothing in VPsPr patients. It is very hard to diagnose and commonly mistaken for CJD or Alzheimer's disease.

Bovine spongiform encephalopathy
Commonly known as mad cow disease, BSE is a prion disease affecting cows. It is extremely rare, however if infected meat and bone meal is fed to cows, it can spread very rapidly. BSE can spread to humans, and is called variant Creutzfeldt-Jakob disease. The UK had an epidemic caused by poor farming practices; meat and bone meal was fed to cows, and when the cows died from the disease, their remains were ground up into more MBM, causing the disease to spread exponentially. Almost a million cows, several cats, and 177 humans died in the epidemic. Worryingly, a new variant of BSE, called atypical BSE, has been shown to be similar to sporadic CJD, however no link has been established between the two.

Scrapie
Scrapie is a TSE affecting sheep and goats. It was the first prion disease ever discovered, in 1755. The signs of scrapie are abnormal gait, ataxia, and compulsive scraping. Scrapie does not appear to be able to infect humans, and the disease has been eradicated in most countries. It is extremely infectious, and a pen that housed infected sheep was disinfected with strong acids, repainted, and the metal was replaced. Sheep placed in it were infected within a year.

Chronic wasting disease
Chronic wasting disease is a TSE affecting deer. The symptoms include severe weight loss, loss of fear of humans, and fur loss. It is the most infectious of all TSEs, and has an R0 of 3.2! Since the disease is 100% fatal, that means for every deer infected, approximately 3-4 deer will die. While this disease doesn't appear to affect humans, there is weak evidence linking it to clusters of CJD cases. While the CDC says that the risk is minimal, it still recommends to take safety precautions, and not to eat infected meat.

Others
Feline spongiform encephalopathy

Ungulate spongiform encephalopathy

Primate spongiform encephalopathy

Ostrich spongiform encephalopathy

Camel spongiform encephalopathy

Transmissible mink encephalopathy

What is not a TSE

 * Alzheimer's disease: While it is a prionopathic dementia with very similar symptoms, and possibly transmissible, it is not a TSE, as the proteins involved are prion isoforms of amyloid-beta and tau, instead of PrPSc. Furthermore, most scientists agree that it is strongly linked to inherited mutations and family history, that can lead to the onset of this disease later in life.
 * Rabies: While the incubation period and symptoms are similar, it is caused by a virus, and not prions.
 * Parkinson's disease: While it's likely a proteopathy, or even a prionopathy, it is definitely not a TSE.
 * Huntington's disease: Likely a prionopathy, but not a TSE.
 * Mad cat disease: While feline spongiform encephalopathy is a TSE, and 'mad cow disease' is too, the so-called 'mad cat disease', is actually caused by a parasite.
 * 2013 novel prion disease : While it's a prion disease involving PrPSc, it is not a TSE, because it is not transmissible, and it doesn't affect the brain.
 * Spongiform-like encephalopathies linked to drug abuse: Not transmissible, and not caused by prions.

Misinformation
Unfortunately, there is a lot of misinformation and discredited science surrounding TSEs.

Spiroplasma
While the scientific consensus is that all TSEs are caused by prions, one scientist has disputed this. Frank O. Bastian has published several papers claiming that the bacterium Spiroplasma is the true cause of TSEs, specifically CWD. The evidence seems convincing - but there are many issues with his research.

No other scientists were able to replicate his findings. In addition, a study done in 2006 directly refutes the theory. While he was able to cause CWD in deer by injecting them with Spiroplasma, he took the bacteria from the brain of deer already infected. The most likely reason for the transmission is contamination of the sample with PrPSc. Any disinfection procedure that would destroy the prions would also kill the bacteria. The bacteria infects plants, and any deer that ate the infected plants would become a carrier. However, they are likely asymptomatic. This explains the presence of the bacteria in CWD-infected deer. Since no uninfected deer were tested, there is no way to prove that the bacteria is only present in cases of CWD.

60,000 cases
A study by Laura Manuelidis showed that 13% of Alzheimer's disease cases were actually CJD. With over 500,000 cases of Alzheimer's per year, that could be up to 60,000 missed cases of CJD, per year. While the study is real, it suffers from a low sample size. They only tested 60 patients. A later study shows that while it is true that there are misdiagnosed CJD cases, the number is far lower. Out of 6,000 cases, 19 cases were shown to be a misdiagnosed TSE. This would put the number at 1,584 more cases, if all 500,000 have the same error rate.

COVID-19 and TSEs
COVID-19 has been linked to TSEs, by both scientists, and cranks.

Acceleration of prion disease pathogenesis
A paper released in July 2020 showed a case of sporadic Creutzfeldt-Jakob disease in a previously healthy man in his 60s, who was infected with COVID-19 when the symptoms started. (improve this plz)

SARS-CoV-2 transmission by prions
Multiple articles from reputable sources have used misleading wording to imply that SARS-CoV-2 uses prions to infect cells. However, what was actually demonstrated was 'prion-like' proteins. The only reasoning for the name is the fact that the N protein can change its folding to adapt to the host's cells. The name 'prion-like' is highly misleading. Prions do not change their folding to adapt to infect proteins. Prions are instead a misfolded version of a host protein, that cause other proteins to change shape. In addition, they generally only infect the same type of proteins that they are a variant of.