The Mad-Cow Disease in Cattle and its Cause

The correct answer to the question is option 'D': Prion.

Introduction to Mad-Cow Disease
Mad-Cow Disease, also known as Bovine Spongiform Encephalopathy (BSE), is a fatal neurodegenerative disease that affects cattle. It is characterized by the accumulation of abnormal prion proteins in the brain and spinal cord, leading to the destruction of nerve tissue.

Explanation of the Correct Answer
The cause of the Mad-Cow Disease is prion rather than a virus, bacteria, or protozoa. Prions are unique infectious agents that consist solely of protein, without any associated genetic material like DNA or RNA. They are derived from a normal cellular protein called PrP (prion protein) that is found in the body of all mammals, including humans and cattle.

The Role of Prions in Mad-Cow Disease
In Mad-Cow Disease, a misfolded form of the PrP protein, known as PrPSc, is responsible for the disease. PrPSc has an abnormal three-dimensional structure compared to the normal PrP protein. When PrPSc comes into contact with the normal PrP protein, it induces a conformational change, causing the normal protein to fold into the disease-causing PrPSc form.

Transmission of Prions
Prions can be transmitted through several routes:
- Ingestion of contaminated feed: The primary route of transmission in cattle is through the consumption of feed that contains prion-infected material, such as meat and bone meal derived from infected animals.
- Maternal transmission: Mad-Cow Disease can also be transmitted from an infected cow to its offspring during pregnancy or through the consumption of infected milk.
- Environmental contamination: Prions can persist in the environment for an extended period, and their transmission can occur through contamination of equipment, facilities, or even soil.

The Impact of Prions on the Brain
Once the abnormal PrPSc proteins accumulate in the brain, they cause a cascade of events that lead to the destruction of nerve cells and the formation of microscopic holes, giving the brain a spongy appearance. This results in the characteristic symptoms of Mad-Cow Disease, including behavioral changes, difficulty in coordination, and eventually, severe neurological impairment.

Conclusion
In conclusion, the Mad-Cow Disease in cattle is caused by prions, which are abnormal, misfolded proteins that induce conformational changes in normal prion proteins. These misfolded proteins accumulate in the brain, leading to the destruction of nerve tissue and the development of the disease. It is important to control the transmission of prions to prevent the spread of Mad-Cow Disease and protect both animal and human health.