Mad cow disease and Creutzfeldt-Jakob disease--is there a link?
Bovine spongiform encephalopathy (BSE), also known as mad cow disease, and variant Creutzfeldt-Jakob disease (CJD) are related disorders. Other TSEs include scrapie (a disease of sheep), feline spongiform encephalopathy, A progressive debilitating neurologic syndrome that is invariably fatal. The report of the Creutzfeldt-Jakob Surveillance Unit from March regarding suggested that a possible link with bovine spongiform encephalopathy (BSE) could not Cattle; Creutzfeldt-Jakob Syndrome/epidemiology; Creutzfeldt-Jakob . CJD is a group of rare diseases called “transmissible spongiform encephalopathies Mad Cow Disease is a progressive neurological (brain) disorder of cattle.
The duration of the disease varies greatly, but sporadic non-inherited CJD can be fatal within months or even weeks. When brain tissue from a person with CJD is examined under a microscopemany tiny holes can be seen where whole areas of nerve cells have died.
The word "spongiform" in " transmissible spongiform encephalopathies " refers to the sponge-like appearance of the brain tissue.
Cause[ edit ] Transmissible spongiform encephalopathy diseases are caused by prions. Prions are proteins that occur normally in neurons of the central nervous system CNS. These proteins, once misfolded, are thought to affect signaling processes, damaging neurons and resulting in degeneration that causes the spongiform appearance in the affected brain. This mass of misfolded proteins disrupts neuronal cell function and causes cell death.
Mutations in the gene for the prion protein can cause a misfolding of the dominantly alpha helical regions into beta pleated sheets. This change in conformation disables the ability of the protein to undergo digestion.
Creutzfeldt-Jakob Disease Fact Sheet | National Institute of Neurological Disorders and Stroke
Once the prion is transmitted, the defective proteins invade the brain and induce other prion protein molecules to misfold in a self-sustaining feedback loop. Once they are formed, abnormal prion proteins aggregate, or clump together. Investigators think these protein aggregates lead to the nerve cell loss and other brain damage seen in CJD. However, they do not know exactly how this damage occurs.
CJD cannot be transmitted through the air or through touching or most other forms of casual contact.
Spouses and other household members of people with sporadic CJD have no higher risk of contracting the disease than the general population. However, exposure to brain tissue and spinal cord fluid from infected persons should be avoided to prevent transmission of the disease through these materials. In some cases, CJD has spread to other people from grafts of dura mater a tissue that covers the braintransplanted corneas, implantation of inadequately sterilized electrodes in the brain, and injections of contaminated pituitary growth hormone derived from human pituitary glands taken from cadavers.
Doctors call these cases that are linked to medical procedures iatrogenic cases.Mad Cow Disease
Sinceall human growth hormone used in the United States has been synthesized by recombinant DNA procedures, which eliminates the risk of transmitting CJD by this route. Many people are concerned that it may be possible to transmit CJD through blood and related blood products such as plasma. Some animal studies suggest that contaminated blood and related products may transmit the disease, although this has never been shown in humans.
Recent studies suggest that while there may be prions in the blood of individuals with vCJD, this is not the case in individuals with sporadic CJD. Scientists do not know how many abnormal prions a person must receive before he or she develops CJD, so they do not know whether these fluids are potentially infectious or not. They do know that, even though millions of people receive blood transfusions each year, there are no reported cases of someone contracting sporadic CJD from a transfusion.
Even among people with hemophilia a rare bleeding disorder in which the blood does not clot normallywho sometimes receive blood plasma concentrated from thousands of donors, there are no reported cases of CJD. While there is no evidence that blood from people with sporadic CJD is infectious, studies have found that infectious prions from BSE and vCJD accumulate in the lymph nodes which produce white blood cellsthe spleen, and the tonsils.
At present, four cases of vCJD infection have been identified following transfusion of red blood cells from asymptomatic donors who subsequently died from vCJD. Recently, one case of likely transmission of vCJD infection by concentrates of blood-clotting protein has been reported in an elderly individual with hemophilia in the United Kingdom. The possibility that blood from people with vCJD may be infectious has led to a policy preventing individuals in the United States from donating blood if they have resided for more than three months in a country or countries where BSE is common.
Both brain biopsy and autopsy pose a small, but definite, risk that the surgeon or others who handle the brain tissue may become accidentally infected by self-inoculation.
Special surgical and disinfection procedures can markedly reduce this risk. How is CJD diagnosed? Several tests can help diagnose CJD.
RT-QuIC is based on an ultrasensitive detection of the pathogenic prion protein in the cerebrospinal fluid of individuals affected by CJD and other forms of human prion diseases. This new advanced test demonstrates a very high sensitivity and specificity of the disease. RT-QuIC differs from traditional surrogate markers of prion disease — and tau proteins—in that it detects directly a disease-defining pathogenic prion protein as opposed to a surrogate marker of rapid neurodegeneration.
Detection of these traditional surrogate marker proteins is accurate in approximately three-fourths of cases. Magnetic resonance imaging MRI has recently been found to be accurate in about 90 percent of cases. The only way to confirm a diagnosis of CJD is by brain biopsy or autopsy.
Mad cow disease and Creutzfeldt-Jakob disease--is there a link?
This procedure may be dangerous for the individual, and the operation does not always obtain tissue from the affected part of the brain. Because a correct diagnosis of CJD does not help the individual, a brain biopsy is discouraged unless it is needed to rule out a treatable disorder.
In an autopsy, the whole brain is examined after death.
Sporadic CJD is most common in people over the age of It occurs when you inherit a mutated gene associated with prion disease from a parent. People with inherited CJD often have family members with the disease. The extent of how CJD manifests in separate family members can vary widely and is known as variable expressivity. However, your risk of eating infected meat is very low. You can also become infected after receiving blood or transplanted tissues, such as a corne, from an infected donor.
Fortunately, there is rigorous sterilization protocols for instruments that have been in contact with tissue at risk for prion exposure, such as brain or eye tissue.
Despite all the press on mad cow disease, vCJD is very rare. Less than 1 percent of people with CJD have the variant type. The risk of classic CJD increases with age.
Creutzfeldt-Jakob Disease | CJD | MedlinePlus
Instead, you need to be exposed to infected bodily fluids or tissue. Caregivers of people with CJD should take extra precautions to lower their risk of contracting the disease: Protect your hands and face from exposure to body fluids.
Make sure to wash your hands, face, and all exposed skin before smoking, eating, or drinking. Use waterproof bandages to cover cuts or bruises.