The Mad Cow Disease In Humans: Variant Creutzfeldt-Jakob Disease

Mad Cow Disease In Humans

Mad cow disease affects the nervous system of cattle. In a few rare cases, it manifests as variant Creutzfeldt-Jakob disease (vCJD) in humans, causing dementia-like symptoms and, eventually, coma and death. Avoid the consumption of beef and beef products in areas prone to the illness to prevent infection. Also, make sure your hospital adheres to strict hygiene standards and correctly disposes off surgical tools.

With sporadic cases of mad cow disease rearing its head across the world, it’s only natural for you to be worried if you are a meat eater. While people who handle infected meat can be at risk, understanding how the disease works in humans and taking adequate precautions is your best line of defense as there is no known cure. Here’s what you need to know about this rare but fatal disease that’s led to casualties among cattle in large numbers and in humans to a lesser extent.

1. Mad Cow Disease May Be Caused By Diseased Proteins Called Prions

Bovine spongiform encephalopathy (BSE), commonly known as mad cow disease, is a disease of the nervous system that primarily affects cattle. It gives their brain a spongy appearance and leads to poor coordination.

It was first identified in 1986 in the United Kingdom via a large outbreak among cattle.1

While the exact cause of BSE is still not clear, diseased proteins called prions may be responsible for the disease. A prion is a normal protein that sometimes folds into an abnormal shape for unknown reasons. It can bind to other proteins of the same type and also force them to change. This chain reaction spreads the disease and continuously creates new infectious material.2 3

2. Mad Cow Disease In Humans Is Variant Creutzfeldt-Jakob Disease (vCJD)

The species barrier prevents mad cow disease from affecting humans in the exact way it affects cattle. But we are susceptible to a variant form of this condition known as variant Creutzfeldt-Jakob disease (vCJD). In fact, scrapie, BSE, and Creutzfeldt-Jakob disease (CJD) are all prion diseases or transmissible spongiform encephalopathies (TSEs). However, scrapie is not known to be transmitted to humans. 4

vCJD is a rare but fatal degenerative condition that affects the brain and causes symptoms like involuntary movement and behavioral changes. When humans are infected, the diseased prions interact with healthy brain prions and force them to act abnormally. Just like BSE, this is a gradual process that finally creates holes in the brain tissue, giving it a sponge-like appearance.5

3. Young Adults Of Both Genders Are Usually At Risk

Individuals who eat beef are at risk of vCJD. If you have visited areas where there has been a breakout of the mad cow disease or regions where there has been a significant number of vCJD cases, then you could be at risk.

As of early 2017, 231 patients across 12 countries have been diagnosed with vCJD. The largest number of cases has occurred in the United Kingdom, followed by France, Spain, Ireland, United States, Italy, the Netherlands, Canada, Portugal, Taiwan, Saudi Arabia, and Japan.6

Young adults of both genders are usually at risk of vCJD. Almost every case of death due to vCJD has been in individuals less than 55 years old. Research indicates that although the reasons for this age distribution is still not well understood, the average age of infection seems to be 26 years among women and 28 years among men. Prion diseases are quite rare in children, hence vCJD is also rare.7

4. Eating Infected Beef And Using Contaminated Instruments May Cause vCJD

Several countries across the world have taken steps to regulate the import of cattle, cosmetics, or supplements from countries affected by the mad cow disease. But though the risk of infection from eating beef products is low, it is not entirely absent.

Eating Infected  Beef Products

Prions can infect humans who are exposed to infected beef products. Prions are concentrated in nervous system tissues and lymphatic tissues of the infected animal. These would include the brain, eye, spinal cord, spleen, bone marrow, and lymph nodes. Such parts are most likely to occur in processed meats such as ground meat, sausages, pastries, and meat pies.8

Eating Meat Contaminated During Handling

While milk or milk products are not harmful, exercise caution while purchasing other beef products. Also note that cooking does not kill prions.

Another mode of infection is eating contaminated meat. At butcher’s shops, whole carcass meat may get contaminated with the infected tissue. Eating this contaminated meat may result in vCJD.9 It is, however, generally considered safe to drink milk and milk products from infected cows.

Blood Transfusion Or Use Of Contaminated Equipment

A few reported cases of vCJD have been traced back to blood transfusions.10 Infection can also be transmitted through contaminated medical instruments, blood products, and organ or tissue grafts since prions are known to attach readily to metal surfaces.11

5. You May Not Show Symptoms Of vCJD Immediately

Since vCJD is still a relatively new disease and every case has ended in death, researchers haven’t yet been able to mark a definite period of incubation. However, diseased prions have been known to live in an individual’s body for as long as 50 years before showing any symptoms.

6. Symptoms Of vCJD Include Behavioral And Psychiatric Changes

However, once the symptoms start to appear, the disease usually runs about 13–14 months on average and leads to a coma-like state in the end.

  • Early symptoms of vCJD include behavioral and psychiatric symptoms such as delusions and mood disturbances.
  • Persistent pain in the lower limbs is another symptom.
  • As the disease progresses, cognition is affected and there is unsteadiness.
  • The disease finally leads to a coma-like state although the length of illness could vary among individuals.12

7. vCJD Can Now Be Diagnosed Through Blood Tests And Tonsil Biopsy

Diagnosis of vCJD is still an uncertain science in most cases. But here are the main tests that will be run by your doctor.

Neuropathologic Exam Of Brain Tissue

The diagnosis of vCJD is usually possible only after a thorough neuropathologic examination of brain tissue. It is important that the condition is diagnosed early in order to get at the real cause of the early dementia-like symptoms. If you suspect vCJD symptoms because you may have worked with cattle or in the meat industry, you need to consult your doctor.13

Blood Screening

In 2011, scientists at the Medical Research Council (MRC), UK, were able to develop a one-of-its-kind blood test to detect variant Creutzfeldt-Jakob disease. The test is designed to pick up the presence of prions in an individual’s blood. The test is 100,000 times more effective than other diagnostic tools because it can detect vCJD before the symptoms begin to show. This is extremely helpful in starting treatment early and even in preventing the spread of the disease by stopping the patient from donating blood.14

Tonsil Biopsy

The tonsil biopsy works almost 100 percent because it is based on the premise that vCJD prions spread over a larger area of tissue when compared with other prion diseases. Since tonsil biopsies indicate the presence of the infection even before the symptoms begin to appear, it is also considered a possible preclinical diagnosis method.15

Process Of Elimination

Elimination of other conditions is often another way to diagnose the condition. It is usually vCJD if:

  • There are signs of a progressive psychotic disorder.
  • Tests do not suggest any other condition with similar symptoms.
  • Symptoms have lasted for over 6 months.
  • There is no evidence of any other prion diseases.
  • EEG (electroencephalography) does not show signs of any other form of CJD. The EEG could, however, be normal or abnormal.16

8. No Proven Cure For vCJD, So Prevention Is Key

Unfortunately, there is no proven cure for vCJD at present. So, treatment usually involves medication targeted at individual symptoms and alleviating discomfort.17 Prevention is the only way.

Choose Meat Products Carefully

  • People who work with cattle or handle cattle meat should maintain high levels of personal hygiene in order to prevent infection.
  • People living in and traveling to places that have had recurrent cases of mad cow disease should be very careful when eating meat and meat products.
  • It is safest to avoid beef and beef products altogether in places that have reported a number of infected cattle as well as vCJD in humans. If you still want to consume beef, stick to muscle meat and steer clear of products with brains and neurological tissue.18

Maintain Hygiene And Screening Standards During Medical Procedures

  • In order to prevent the transmission of the infection during medical procedures, make sure your hospital adheres to strict hygiene standards and disposes of surgical tools, needles, and other instruments after a single use.
  • To prevent the disease from spreading through blood transfusion, people with a family history of vCJD are not eligible for blood donation. This also includes people who may have received a blood donation in the UK since 1980 or if they have even lived in the UK between 1980 and 1996, when a massive mad cow disease epidemic took place in the UK.19

Most countries have taken steps to prevent the entry of BSE-infected tissue in the food supply through tight restrictions on animal feed, monitoring of cattle health, strict regulations on the import of cattle, and restrictions on what parts of cattle can be processed for food. However, exercising caution on a personal level is your best bet when it comes to prevention.

References   [ + ]

1. “Bovine Spongiform Encephalopathy in a Dairy Cow — Washington State, 2003.” Centers for Disease Control and Prevention 52, no. 53(2004): 1280-1285.
2, 8. Mad Cow Disease. University of California San Francisco.
3. What Is a Prion?. Scientific American.
4. Variant Creutzfeldt-Jakob Disease (vCJD). Centers for Disease Control and Prevention.
5, 9, 15. Trevitt, Clare R., and Singh, Pramil N. “Variant Creutzfeldt-Jakob disease: pathology, epidemiology, and public health implications.” The Americal Journal of Clinical Nutrition 78, no. 3 (2003):651S-656S.
6. Risk for Travelers. CDC.
7. de Villemeur, Thierry Billette. “Creutzfeldt–Jakob disease.” In Handbook of clinical neurology, vol. 112, pp. 1191-1193. Elsevier, 2013.
10, 12. Acquired prion disease. MRC Prion Unit, University College London (UCL).
11. Edgeworth, Julie Ann, Michael Farmer, Anita Sicilia, Paul Tavares, Jonathan Beck, Tracy Campbell, Jessica Lowe et al. “Detection of prion infection in variant Creutzfeldt-Jakob disease: a blood-based assay.” The Lancet 377, no. 9764 (2011): 487-493.
13. Variant Creutzfeldt-Jakob Disease (vCJD). Centers for Disease Control and Prevention.
14. World’s first blood test for vCJD developed in MRC lab. Medical Research Council Prion Unit.
16. Creutzfeldt-Jakob disease (CJD) and variant CJD (vCJD). World Health Organisation.
17. Variant Creutzfeldt-Jakob Disease (vCJD). Centers for Disease Control and Prevention.
18. Brown, Paul, Will, Robert G., Bradley, Raymond, Asher, David M., and Detwiler, Linda. “Bovine Spongiform Encephalopathy and Variant Creutzfeldt-Jakob Disease: Background, Evolution, and Current Concerns.” Emerging Infectious Diseases 7, no. 1 (2001): 6-16.
19. Brown, P. “The risk of bovine spongiform encephalopathy (‘mad cow disease’) to human health.”American Medical Association 278, no. 12 (1997):1008-11.

Disclaimer: The content is purely informative and educational in nature and should not be construed as medical advice. Please use the content only in consultation with an appropriate certified medical or healthcare professional.