When parasite expert Kevin Kazacos looked into a die-off at a chicken farm in Indiana in 1979, he found it "dramatic, so pathogenic, it looked like nothing I'd dealt with before.


In 1980, he saw the first confirmed human death, a Pennsylvania boy who apparently had eaten feces from raccoons living in the family's chimney. Like the birds, the boy had neurological problems and trouble controlling his muscles. The autopsy showed roundworm larvae in his brain.