"Imagine microscopic worms living in the soil. They enter your body through your bare feet, travel to your intestines, and stay there for years sucking your blood like vampires. You feel exhausted. You get sick easily. It sounds like a nightmare, but that's what happened in the American South during the 1800s and early 1900s. Doctors never guessed that hookworms were making patients ill, but zoologist Charles Stiles knew better. Working with one of...