20.1 Viruses
20.2 Prokaryotes
20.3 Diseases Caused by Bacteria and Viruses
THE MAD COWS
In 1986, something strange began to happen to cattle in Great Britain. Without warning, the animals began acting strangely, losing control of their movements, staggering and stumbling, and eventually dying. Farmers watched helplessly as the disease they called “mad cow” spread through their cattle. The disease affected more than 30,000 cattle in 1991.
Studies of the brains of cattle killed by mad cow disease showed that large areas of the animals' brains had been destroyed. Under the microscope, the holes in the tissue made the brain resemble a sponge. Because of this, the disease was given the name bovine spongiform encephalopathy, or BSE. But the cause of the disease was a mystery. As you read this chapter, look for clues that explain the culprit behind this disease. Then, solve the mystery.
Never Stop Exploring Your World.
Finding what caused this disease is only the beginning. Take a video field trip with the ecogeeks of Untamed Science to explore the other side of the story—you'll see that not all microbes are “bad.”