Mad cow disease in the cattle is caused by

🔑 Explanation
→ The bovine spongiform encephalopathy (BSE), commonly called "mad cow disease" in cattle, and its analogous variant Cr–Jacob disease (CJD) in humans is caused by prions.
→ Prions are infectious agents similar in size to viruses that cause the transmission of several infectious neurological diseases.
→ These differ from viruses by having an abnormally folded protein.
→ Prions were named by Stanley Prusiner.

📌 Important Points
→ Mad cow disease is a progressive neurological disorder in which cattle experience trouble while walking, weight loss, and show abnormal behaviour.

📝 Additional Information
→ Virus:
→ Viruses are non-cellular organisms characterised by an inert crystalline structure outside the living cell.
→ The name virus, meaning venom or poisonous fluid, was given by Dmitri Ivanowsky (1892).
→ Viruses are largely made up of proteins, and also contain genetic material, which could be either RNA or DNA.
→ Viruses cause diseases like mumps, smallpox, herpes, and influenza. AIDS in humans is also caused by a virus. In plants, symptoms can include mosaic formation, leaf rolling, yellowing, vein clearing, dwarfing, and stunted growth.

→ Viroid:
→ Viroids are infectious agents that consist of nucleic acid (ssRNA) in their genome but lack a protein coat.
→ Viroids were first discovered by T.O. Diener (1971), who observed that these were smaller than viruses and caused potato spindle tuber disease.

→ Bacteriophage:
→ A bacteriophage is a virus that infects bacteria.
→ Bacteriophage was discovered by Twort & Felix.
→ A bacteriophage consists of proteins that encapsulate a DNA or RNA genome.