Mad Cow Disease

Other Names: Creutzfeldt-Jakob disease (CJD) or Bovine spongiform encephalopathy (BSE)

Description:
Mad cow disease is a degenerative brain disorder that leads to dementia and, ultimately, death. Symptoms of the disease is dementia-like brain disorders, such as Alzheimer’s. But mad cow disease usually progresses much more rapidly.

It captured public attention in the 1990s when some people in the United Kingdom developed a form of the disease after eating meat from diseased cattle.
Mad cow disease is thought to be due to an infection by a misfolded protein, known as a prion. Cattle are believed to have been infected by being fed meat-and-bone meal (MBM) that contained the remains of other cattle who spontaneously developed the disease or scrapie-infected sheep products. The outbreak increased throughout the United Kingdom due to the practice of feeding meat-and-bone meal to young calves of dairy cows. Cases are suspected based on symptoms and confirmed by examination of the brain. Cases are classified as classic or atypical, with the latter divided into H- and L types. It is a type of transmissible spongiform encephalopathy (TSE).

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The time between infection and onset of symptoms is generally four to five years. Time from onset of symptoms to death is generally weeks to months. Spread to humans is believed to result in variant Creutzfeldt–Jakob disease (vCJD)

Although serious, CJD is rare, and vCJD is the least common form. Worldwide, there is an estimated one case of CJD diagnosed per million people each year, most often in older adults.

Symptoms:
Mad cow disease is marked by rapid mental deterioration, usually within a few months. Initial signs and symptoms typically include:

  • Personality changes
  • Anxiety
  • Depression
  • Memory loss
  • Impaired thinking
  • Blurred vision or blindness
  • Insomnia
  • Difficulty speaking
  • Difficulty swallowing
  • Sudden, jerky movements

As the disease progresses, mental symptoms worsen. Most people eventually lapse into a coma. Heart failure, respiratory failure, pneumonia or other infections are generally the cause of death. Death usually occurs within a year.

In people with the rarer vCJD, psychiatric symptoms may be more prominent in the beginning, with dementia — the loss of the ability to think, reason and remember — developing later in the illness. In addition, this variant affects people at a younger age than classic CJD does and appears to have a slightly longer duration — 12 to 14 months.

Causes:
Mad cow disease is an infectious disease believed to be due to a misfolded protein, known as a prion. Cattle are believed to have been infected from being fed meat and bone meal (MBM) that contained the remains of other cattle who spontaneously developed the disease or scrapie-infected sheep products. The outbreak increased throughout the United Kingdom due to the practice of feeding meat-and-bone meal to young calves of dairy cows.

Prions replicate by causing other normally folded proteins of the same type to take on their misfolded shape, which then go on to do the same, leading to an exponential chain reaction. Eventually, the prions aggregate into an alpha helical, beta pleated sheet, which is thought to be toxic to brain cells.

The agent is not destroyed even if the beef or material containing it is cooked or heat-treated. Transmission can occur when healthy animals come in contact with tainted tissues from others with the disease. In the brain, the agent causes native cellular prion protein to deform into the misfolded state, which then goes on to deform further prion protein in an exponential cascade. This results in protein aggregates, which then form dense plaque fibers. Brain cells begin to die off in massive numbers, eventually leading to the microscopic appearance of “holes” in the brain, degeneration of physical and mental abilities, and ultimately death.

The agent can be transmitted to humans by eating food contaminated with it. The highest risk to humans is believed to be from eating food contaminated with the brain, spinal cord, or digestive tract though any tissue may be involved.

However, “classic”mad cow disease hasn’t been linked to contaminated beef.

Diagnosis:
Diagnosis of mad cow disease continues to be a practical problem. It has an incubation period of months to years, during which no signs are noticed, though the pathway of converting the normal brain prion protein (PrP) into the toxic, disease-related PrPSc form has started. At present, virtually no way is known to detect PrPSc reliably except by examining post mortem brain tissue using neuropathological and immunohistochemical methods. Accumulation of the abnormally folded PrPSc form of PrP is a characteristic of the disease, but it is present at very low levels in easily accessible body fluids such as blood or urine. Researchers have tried to develop methods to measure PrPSc, but no methods for use in materials such as blood have been accepted fully.[by whom?]

The traditional method of diagnosis relies on histopathological examination of the medulla oblongata of the brain, and other tissues, post mortem. Immunohistochemistry can be used to demonstrate prion protein accumulation.

In 2010, a team from New York described detection of PrPSc even when initially present at only one part in a hundred billion (10?11) in brain tissue. The method combines amplification with a novel technology called surround optical fiber immunoassay and some specific antibodies against PrPSc. After amplifying and then concentrating any PrPSc, the samples are labelled with a fluorescent dye using an antibody for specificity and then finally loaded into a microcapillary tube. This tube is placed in a specially constructed apparatus so it is totally surrounded by optical fibres to capture all light emitted once the dye is excited using a laser. The technique allowed detection of PrPSc after many fewer cycles of conversion than others have achieved, substantially reducing the possibility of artifacts, as well as speeding up the assay. The researchers also tested their method on blood samples from apparently healthy sheep that went on to develop scrapie. The animals’ brains were analysed once any signs became apparent. The researchers could, therefore, compare results from brain tissue and blood taken once the animals exhibited signs of the diseases, with blood obtained earlier in the animals’ lives, and from uninfected animals. The results showed very clearly that PrPSc could be detected in the blood of animals long before the signs appeared. After further development and testing, this method could be of great value in surveillance as a blood- or urine-based screening test for BSE or mad cow disease.

Treatmen:
No effective treatment exists for mad cow disease or Creutzfeldt-Jakob disease or any of its variants. A number of drugs have been tested and have not shown benefits. For that reason, doctors focus on alleviating pain and other symptoms and on making people with these diseases as comfortable as possible.

Prevention:
A ban on feeding meat and bone meal to cattle has resulted in a strong reduction in cases in countries where the disease has been present. In disease-free countries, control relies on import control, feeding regulations, and surveillance measures.

In UK and US slaughterhouses, the brain, spinal cord, trigeminal ganglia, intestines, eyes, and tonsils from cattle are classified as specified risk materials, and must be disposed of appropriately.

An enhanced BSE-related feed ban is in effect in both the United States and Canada to help improve prevention and elimination of BSE.

Disclaimer: This information is not meant to be a substitute for professional medical advise or help. It is always best to consult with a Physician about serious health concerns. This information is in no way intended to diagnose or prescribe remedies.This is purely for educational purpose.

Resources:
https://en.wikipedia.org/wiki/Bovine_spongiform_encephalopathy
https://www.mayoclinic.org/diseases-conditions/creutzfeldt-jakob-disease/symptoms-causes/syc-20371226

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