Proteins that cause disease in humans and animals are called:

Explanation

Prions are misfolded proteins that can induce other proteins to also misfold, leading to the accumulation of abnormal protein structures in cells. This can result in neurodegenerative diseases, such as Creutzfeldt-Jakob disease in humans and mad cow disease in cattle. Prions are unique because they can propagate without nucleic acids (DNA or RNA), making them distinct from other infectious agents like bacteria and viruses.