These days, every disease has its animal mascot: There’s the civet for SARS, the chicken for the avian flu, the prairie dog for monkeypox, and, of course, the cow for mad cow disease (also known ...

In 1987, government epidemiologist John Wilesmith was tasked with a secret mission: to find out why cows were suddenly going mad, and how the madness was spreading. He looked for links to vaccines ...