Zombies may still be a thing of fiction, but some parasites more or less turn their hosts into the walking dead.

These masters of mind control manipulate their hosts from within, causing them to act in self-destructive ways that ultimately benefit the parasite. (Read "Mindsuckers" in National Geographic magazine.)

"Some parasites can alter the behavior of their host in ways that give the parasite a better home, or provide more nutrients, or cause the host to move to a different environment," said Janice Moore, a biologist at Colorado State University in Fort Collins.

This strategy seems to work, she added: "A parasite that can alter the behavior of its host, and in doing so improve its own transmission, is