Hint:Mad cow disease is a neurodegenerative disease commonly seen in cattle, that may spread to humans. The symptoms of this disease included abnormal behaviour, weight loss and also difficulty in walking.
Complete answer: Let's have a look at the details of mad cow disease. Bovine spongiform encephalopathy, also known as mad cow disease is a brain disorder in adult cattle, that can spread to humans through the diseased meat. Mad cow disease is caused by a misfolded protein, known as a prion. Prions have the ability to transmit their misfolded structure into normal variants of the same protein. Symptoms of mad cow disease include abnormal behaviour, weight loss etc. Due to the extremely long incubation period of the disease, symptoms are not seen immediately.
Now, let's look at the options for finding the correct answer. >Option B: Mad cow disease is caused by prions. Therefore, this is the correct option. >Option A, C, D are the incorrect options.
Additional information: Prions replicate by causing the misfolding of other normal proteins, which then go on to do the same, thus by initiating a chain reaction. By time, prions aggregate into alpha helical and beta pleated sheets, which will result in the damage of brain cells. Transmission of the disease occurs when the healthy animals come in contact with tissues of other affected animals. As a result of this disease, brain cells begin to die off in huge numbers and eventually leads to microscopic appearances in the brain and results in the damage of physical and mental health and ultimately death.
Thus, the correct answer is option (B) Prion.
Note:At times, it is seen that mad cow disease spread from cows to humans, believed to result in variant Creutzfeldt–Jakob disease. It can cause serious psychiatric problems and behavioural changes in humans.