Mad cow disease is cause by an infectious agent ( called prions) that is most concentrated in the nervous tissue.

Experts believe that the fatal disease it is caused by aberrant proteins called infectious prions, which leave the brain with spongelike holes.

All are believed to be caused by aberrant proteins called prions.

The members of this genus and the Blue Petrel form a sub-group called prions.

The diseases are caused by aberrant proteins called prions, which leave the brain riddled with holes.

Scientists think the infections are caused by abnormal proteins called prions, which trigger other proteins in the brain to change shape.

These self-propagating protein aggregates are called prions and constitute the basis of prion diseases.

It is caused by proteins called prions.

It is caused by special proteins called prions, and it always leads to death.

It is classified as a transmissible spongiform encephalopathy, believed to be caused by proteins called prions.