A cow infected with BSE has difficulty holding up its head. Its muscles twitch uncontrollably. It stumbles and falls. Eventually, it loses the ability to walk. Soon after, it dies.
People who eat meat from a cow infected with BSE can have similar symptoms. Their brain tissue gets spongy, resulting in dementia. That's a nerve disorder that causes loss of perception, memory, and judgment. After a while, they become paralyzed–and then die.
—When Birds Get Flu and Cows Go Mad! How Safe Are We?, John DiConsiglio
What is the main problem stated in this excerpt?
Cows can’t hold their heads up and fall down.
Brain tissue gets spongy.
BSE causes death in humans and cows.
Cows die from the disease.