Bovine Disease (Mad Cow Disease)

Bovine Disease (Mad Cow Disease)
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Bovine disease, also known as mad cow disease or Bovine spongiform encephalopathy (BSE), is a degenerative disease that affects the central nervous system of cattle. This disease is known to be contagious and slowly progressive.

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Experts believe that the causative agent of this disease is due to an altered form of protein that is generally found on cell surfaces, called a prion. It is still unknown why and how this protein mutates and destroys nervous system tissue.

Symptoms of this degenerative disease include weight loss, abnormal behaviour, and trouble walking. Because this disease progresses slowly, it takes about four to five years before these symptoms are noticed.

Then, it takes between a couple of weeks to a few months before the cow will die after the symptoms have manifested. Bovine disease is also zoonotic, meaning that it can transmit from animal to human.

Table of Contents

Symptoms of bovine disease

The symptoms of the bovine disease are not apparent immediately in cattle. This is because the disease has a long period of incubation. Infected cattle have been found to show the following:

  • Abnormal gait: This disease affects the coordination and balance of the infected animals. Since the hindlimb ataxia affects the animal’s gait, this occurs when the animal loses muscle control. This results in impaired coordination and awkward gait.
    Abnormal behavior: Certain behavioral changes may be noticed, and they include aggression, anxiety towards certain situations, nervousness, and an overall shift in temperament.

Other non-specific symptoms have also been observed, and they include:

  • Significant weight loss
  • Reduction in milk production
  • Lameness
  • Ear infections
  • Teeth gritting due to pain

Other rare but recently observed symptoms also include persistent pacing, rubbing, and licking. Some livestock may experience a combination of the symptoms listed above, while others may only show one of these symptoms.

Once these clinical signs start, they only worsen over-time, subsequently causing recumbency, coma, and ultimately death.

Causes of bovine disease

The bovine disease is believed to be due to a mutated protein in the brain cell called a prion. Cattles are suspected to be infected by consuming “Meat and Bone Meal (MBM)” that contains remains of bovine-disease-infected cattle.

There have been cases of cattle being infected by bovine disease because they were fed scrapie-infected sheep products.

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Outbreaks are usual after having young calves of dairy cows consume poorly processed meat-and-bone meal. Altered proteins in the brain cells, called prions, replicate by causing the same type of proteins, which are typically folded to become misfolded.

Prions spread across the tissue by forcing other normal proteins to become misfolded. This goes on, causing a chain reaction that eventually progresses to an alpha-helical and beta-pleated sheet.

These are aggregated forms of prions that are considered to be toxic to brain cells. This can cause death to the brain cells of the infected in large numbers, thereby resulting in microscopic holes in the brain. This subsequently leads to the degeneration of the mental and physical abilities of the animal and death.

This infectious agent cannot be destroyed by heat. Therefore, even if you have your infected beef products cooked, roasted, or fried, you can still get infected. Healthy livestock can also get infected when it comes in contact with infected tissues of another infected animal.

Bovine disease or mad cow disease in humans

Bovine Disease (Mad Cow Disease)
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The version of Bovine disease that affects humans is known as variant Creutzfeldt-Jakob disease (vCJD). Research suggests that the cause could be as a result of consuming beef products contaminated with the causative agent from infected livestock.

The beef products can be contaminated with tissues of the central nervous system such as the spinal cord and the brain of an infected animal. This is why it is recommended to dispose of the brains and spinal cord materials of cattle that are suspected to be infected.

This disease can affect people of all age groups. The symptoms of the early stages of variant Creutzfeldt-Jakob disease include depression and loss of coordination. The symptoms of later stages include dementia develops.

The advanced stages of vCJD are fatal, and only at this stage are the abnormalities of the brain detectable by Magnetic Resonance Imaging (MRI).

Diagnosis

Diagnosing bovine disorder is quite difficult since it has an extremely long incubation period. During this incubation, no symptoms are found while the infectious agent spread through the brain, causing microscopic holes to spread as well.

Currently, there is no reliable way of detecting toxic altered brain protein. One way of knowing is adopting neuropathological and immunohistochemical steps to examine the post mortem brain tissue. The histopathological tests are used to examine the medulla oblongata of the brain, and other tissues, post mortem.

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At the same time, the immunohistochemistry method is used to determine prion protein accumulation. These are the classical ways of diagnosing this infection. Accumulated abnormally folded Prions are present at a very low amount in body fluids that are easily accessible such as blood or urine.

Attempts have been made to develop methods to determine the number of prions in the system, but no methods have been formed. This is because the use of materials such as urine and blood has not been entirely accepted.

Classification

Bovine disease is an infectious disease that majorly affects the central nervous system of infected animals. This infection comes in the form of transmissible spongiform encephalopathies such as Creutzfeldt–Jakob disease, kuru in humans, the chronic wasting disease in deer, and scrapie in sheep.

Prevention

The government has a massive role to play to prevent an outbreak. They should place a ban on the importing meat-and-bone meal from countries or states with recorded cases already.

Feeding regulations and surveillance measures should be enforced. For example, slaughterhouses should be encouraged to have the brain, eyes, intestines, tonsils, trigeminal ganglia, and the spinal cord to be appropriately gotten rid of.

Sources          

  • Bovine spongiform encephalopathy; Wikipedia
  • The Basics of Mad Cow Disease; Webmd
Bovine Disease (Mad Cow Disease)
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