Was mad cows disease caused by fungus?

No, mad cow disease (Bovine Spongiform Encephalopathy, or BSE) was caused by a specific type of abnormal protein called a prion. Unlike typical infectious agents such as bacteria or viruses, prions do not contain any genetic material like DNA or RNA. They are composed solely of misfolded proteins that can spread within the brain and cause progressive damage to the nervous system. Mad cow disease is a fatal neurodegenerative disorder that affects cattle and is characterized by the accumulation of abnormal prion proteins in the brain. It belongs to a group of transmissible spongiform encephalopathies (TSEs) that include other related diseases such as scrapie in sheep and Creutzfeldt-Jakob disease (CJD) in humans.