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Mad Cow Disease Bovine Spongiform Encephalitis BSE FAQ


Mad Cow Disease Bovine Spongiform Encephalitis (BSE)

BSE is also known as bovine spongiform encephalopathy (BSE). Its pathogen is neither bacteria nor virus in the traditional sense, and it does not even contain genetic material-nucleic acid. At present, most of the pathogens are called prion, and the symptoms are similar to pruritus of sheep, commonly known as mad cow disease. 

The brain tissue of the diseased cow is spongy, with symptoms of unstable gait, imbalance, itchiness, restlessness, etc. It usually dies within 14 to 90 days. Due to different types, the incubation period of mad cow disease is different, generally between 2 and 30 years. 

The disease was first discovered in the United Kingdom in April 1985 and was named BSE in November 1986. BSE is not only widespread in the UK, but cases have also been reported in many other countries and regions. The disease is now spreading globally.

Thematic content on BSE


Incidence

BSE was first discovered in the UK in April 1985 and was diagnosed as BSE by pathology in 1986. Since then, the number of BSE cases has been increasing. In 1989, Mad Cow Disease first appeared in a country outside of England (Iceland). Since then, cases of BSE have been reported in Northern Ireland, Ireland, Portugal, Switzerland, France, Belgium, Denmark, Germany, Luxembourg, Netherlands, Spain, Liechtenstein, Italy and other countries. 

In 2001, Japan discovered the first mad cow disease in Asia; in 2002, Israel discovered the first mad cow disease in the country; in 2003, Canada discovered the first mad cow disease in North America. 

Since 1985, mad cow disease has occurred in 26 countries around the world. Among them, 490 cases of mad cow disease occurred in 19 countries around the world in 2005.

377 cases of mad cow disease occurred in 12 countries around the world in 2006.

Fortunately, in Asia there are negligible chances and China has not yet discovered BSE.

Infection: Mad Cow Disease

Pathogen

Prions are abnormal proteins formed by certain glycoproteins (PrPc, which can be hydrolyzed by proteases) on the surface of normal host nerve cells (PrPsc, which cannot be hydrolyzed by proteases after translation). Different secondary structure). 

Prions can cause bovine spongiform encephalopathy, with a mortality rate of up to 100%, and can also cause human Kuru, Creutzfeldt-Jakob disease (CJD), Gehr-Sherman syndrome (GSS) and lethal families Eye loss, sheep pruritus in animals, infectious encephalopathy in mink, chronic atrophy of deer, etc.

The pathogen is highly resistant to physicochemical factors such as ultraviolet rays, ionizing radiation, ultrasonic waves, non-ionic detergents, proteases, etc.

 It cannot be completely inactivated by high temperature, and ethanol, formalin, hydrogen peroxide, phenol, etc. Inactivate it.

However, it can be inactivated by treatment with 2% to 5% sodium hypochlorite or 90% carbolic acid for 24 hours, and protein denaturants such as SDS, urea, and phenol can inactivate it.

CSF is non-immunogenic, does not cause fever, no inflammatory reaction, and no immune response after infection. 

The cause of the disease is the infectivity of the brain, cervical spinal cord, spinal cord end and retina and other tissues, less in the spleen, lymph nodes, muscles and blood, and feces and urine are almost infectious.

Popular features of Mad Cow Disease

What is the source of  BSE infection?

At present, it is generally believed that the main reason for the large-scale outbreak of BSE is due to the consumption of meat and bone meal (MBM) containing cattle scrapie prions, which is a large amount of sheep on stock.
Imported animals and animal products contaminated with pruritus pruritus.
 Processing methods for meat and bone meal failed to inactivate prions.  
Feeding cattle with meat and bone meal for ruminants. 
However, some scholars believe that the cause of BSE is related to mites living in hay. 
After injection of chemicals extracted from mites, mice can develop itch.
Microscopic View of Mad Cow Disease Virus
   

What is the way for spreading of Mad Cow Disease?

The pathogen of mad cow disease is mainly generated from the carcasses of sick cattle and sick sheep, and is transmitted through the food chain; recent studies have found that BSE can be transmitted by maternal sources, but the probability is lower. 
This method alone does not seem to be sufficient to continue the epidemic of BSE.

At present, there has not been any mutual infection of mad cow disease among individuals in the herd, that is, no horizontal transmission has been found.
   

What is the BSE Incubation period and age of onset?

  BSE incubation period is 2-8 years, with an average of 4-5 years. The age of onset cattle is mostly 4-6 years old, rare under 2 years old. 
Beginning in October 2000, the EU bans the sale of bone-in meat for cattle aged 12 months and older
   

Susceptible animals

Domestic cattle, dairy cows, bison, antelope, etc. are susceptible. Feline animals such as domestic cats, tigers, leopards, mink, lions and other carnivores also have certain susceptibility.
  

What are the Clinical Symptoms of Mad Cow Disease?

This disease mostly occurs in adult cattle around 4 years old. Symptoms vary. 
Most sick cows have changes in the central nervous system, abnormal behavior, irritability, excessive sensitivity to sound and touch, especially head touch, unstable gait, frequent kicks and even falls and convulsions.
 
In the late period, there was tonic spasm, hard stools, symmetrical movements in both ears, slow heartbeat, increased respiratory rate, weight loss, extreme weight loss, and even death.

It is not only cows that are affected by mad cow disease. People who eat contaminated beef, bovine spinal cord, etc. may also be infected with the new fatal Creutzfeldt-Jakob disease. 

A spongy cavity will appear in the brain of the patient, which first shows anxiety, and then leads to memory loss, dysfunction of the body, and eventually mental confusion or even death.
  

Pathological changes

Not obvious to the naked eye. The main pathological change of histological examination is that the brain tissue has a sponge-like appearance (cavitation of brain tissue).

The brainstem gray matter undergoes bilateral symmetrical spongy degeneration and contains varying amounts of vacuoles in the nerve fiber network and nerve cells. There is no inflammation.

What is the diagnosis method of Mad Cow Disease?

    According to the characteristics of clinical symptoms and epidemiological characteristics can make a preliminary diagnosis of mad cow disease. 
Because the disease has neither an inflammatory response nor an immune response, it has been difficult to diagnose serology so far. Therefore, qualitative diagnosis is currently based on brain histopathological examination. 

According to Well et al. (1989), changes in vacuoles in the brainstem region, especially in the nucleus oblongata and trigeminal spinal nucleus, the accuracy of diagnosing BSE is as high as 99.6%. 

Vascularization of brainstem neurons and neural fiber network is of pathogenic significance.

 For laboratory diagnosis, such as animal infection test, PrPsc immunological test and SAF test, etc., please refer to the itch.

Prevention of Mad Cow Disease

What is the Prevention Method against Mad Cow Disease?

The body does not produce a protective immune response to BSE infection. Therefore, immunization is not an ideal way to prevent BSE. There are two international transmission routes for BSE: importing live cattle and their products or contaminated feed in countries or regions with BSE disease; importing live sheep and their products or contaminated feed in countries or regions with itchy disease.

 

The current international preventive and control measures are:


    (1) Embargoed beef products in epidemic-free areas:

 A comprehensive ban on live cattle, cattle embryos, semen, milk products, by-products, etc. from countries and regions in BSE-endemic areas.

    (2) Establish an epidemic report system:

 once a suspected BSE disease is found, it must be reported to the government's competent veterinary department in time.

    (3) Slaughter and safe destruction

All cattle and other animals infected with BSE are slaughtered and safely destroyed.

    (4) Forbidden for Humans

It is forbidden for humans and animals to consume animal feeds and internal organs that may be vectored over 6 months of age.

    (5) Strict feed processing regulations

Prohibiting the use of meat and bone by-products such as cattle and sheep and other animals as feed additives for ruminants.

What is the harm from Mad Cow Disease?

 1. Harm to human economic and social development

 In the international agricultural trade, the risk status of animal epidemics such as mad cow disease in one country has become an important means for other countries to impose trade barriers on it. 

The sending of mad cow disease has caused a heavy blow to the world's cattle industry. 

At present, although there is no BSE outbreak in Asia, from the analysis of the pathogenesis of BSE, the current status of animal husbandry development and the history of Asia's animal husbandry international trade.

There is still a risk of BSE transmission in Asia. The basic level of domestic animal husbandry production should also strengthen the understanding of BSE, animal husbandry. And the grassroots level of feed supervision should strengthen the effective and rapid detection methods for mad cow disease.

 2. Harm to human health

 The study found that the spread of human Creutzfeldt-Jakob disease is closely related to the consumption of food contaminated with BSE factors. The source of the disease first enters the local lymphatic tissue of the intestine and proliferates therein, and finally locates in the central nervous system. Since 1995, there have been 11 cases of human infection in the world, with a mortality rate of about 95%. 

According to statistics from British scientists, about 4,000 people in the UK are carriers of the prion virus, and about 20 people die of mad cow disease each year.
In addition, the disease protein of Alzheimer's disease and the BSE virus protein are surprisingly similar. 
Therefore, research on the prevention and control of mad cow disease is conducive to the prevention and diagnosis of human mental diseases such as Creutzfeldt-Jakob disease and Alzheimer's disease.

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