Fact: nature makes zombies out of the living. Mind and body control is what parasites are after in the animals they infect, effectively turning their hosts into —sounds familiar? —zombies.
For instance, Gypsy moth caterpillars infected with the baculovirus virus climb to the top of trees and clamp onto leaves until they die and liquefy, raining down viruses to infect other caterpillars in the forest, while the spinochordodes tellinii hairworm infects grasshoppers and crickets, making them kill themselves by jumping into water, where the worm want to find a mate at. Parasites creep the hell out of us.