Summary about Disease
Bovine Spongiform Encephalopathy (BSE), commonly known as Mad Cow Disease, is a fatal neurodegenerative disease in cattle that causes a spongy degeneration of the brain and spinal cord. It is a prion disease, meaning it is caused by an abnormal, misfolded protein called a prion. It belongs to a group of diseases called transmissible spongiform encephalopathies (TSEs). While primarily affecting cattle, BSE has implications for human health through the related human prion disease, variant Creutzfeldt-Jakob Disease (vCJD), which can be contracted by consuming BSE-contaminated beef products.
Symptoms
In cattle, symptoms of BSE include:
Changes in temperament, such as nervousness or aggression
Abnormal posture
Incoordination and difficulty walking
Decreased milk production
Weight loss despite normal appetite
Behavioral changes These symptoms typically develop gradually over several weeks to months.
Causes
BSE is caused by a misfolded protein called a prion. The infectious prion (PrPSc) is believed to arise from a change in the normal prion protein (PrPC) found in the brain and nerve cells. The primary route of transmission in cattle was the consumption of feed contaminated with the rendered remains of other cattle (meat-and-bone meal) that contained BSE prions. Regulatory measures now prohibit the use of ruminant-derived protein in ruminant feed in many countries.
Medicine Used
There is no cure or treatment for BSE in cattle. Once the disease develops, it is invariably fatal. Management focuses on preventing the spread of the disease through strict control measures.
Is Communicable
BSE is not directly communicable from one cow to another through casual contact. The primary mode of transmission is through the ingestion of contaminated feed. Variant Creutzfeldt-Jakob disease (vCJD) in humans is linked to the consumption of BSE-contaminated beef products. Human to human transmission of vCJD is extremely rare, but has been documented in cases of blood transfusions and contaminated surgical instruments.
Precautions
Precautions to prevent BSE and vCJD include:
Banning the use of ruminant-derived protein in ruminant feed: This is the most critical step in preventing the spread of BSE.
Surveillance programs: Testing cattle for BSE to detect and remove infected animals.
Proper disposal of infected animals: Preventing BSE prions from entering the food chain or environment.
Stringent hygiene practices in slaughterhouses: Minimizing the risk of contamination of meat products.
Avoiding consumption of high-risk tissues (brain, spinal cord, tonsils, ileum) of cattle: These tissues are most likely to harbor BSE prions.
How long does an outbreak last?
The duration of a BSE outbreak can vary greatly depending on the effectiveness of control measures. Once strict feed bans are implemented, it can take several years to see a significant decline in the number of BSE cases because of the long incubation period of the disease. Outbreaks are considered to be under control when the incidence of BSE cases declines substantially and consistently over time.
How is it diagnosed?
BSE is typically diagnosed post-mortem through laboratory testing of brain tissue. The most common diagnostic tests include:
Immunohistochemistry: Detects the presence of abnormal prion protein in brain tissue.
Western blot: Identifies the abnormal prion protein based on its molecular weight.
ELISA (Enzyme-Linked Immunosorbent Assay): Used for screening large numbers of samples.
Histopathology: Examining brain tissue under a microscope for characteristic spongiform changes. Ante-mortem (before death) diagnostic tests are not reliable for BSE.
Timeline of Symptoms
The incubation period for BSE is typically 2 to 8 years, meaning it can take that long for symptoms to appear after initial infection. The clinical phase, during which symptoms are observed, usually lasts from 2 weeks to 6 months. The symptoms progress gradually, starting with subtle behavioral changes and progressing to more severe neurological signs.
Important Considerations
Public Health Impact: While BSE primarily affects cattle, the potential for transmission to humans via vCJD makes it a significant public health concern.
Economic Impact: BSE outbreaks can have devastating economic consequences for the beef industry, leading to trade restrictions and consumer concerns.
Ongoing Research: Research is ongoing to better understand prion diseases, develop effective diagnostic tests, and explore potential therapeutic interventions.
International Collaboration: International collaboration is essential for monitoring and controlling BSE globally.