Parasites can highjack hosts' nervous systems, making them into walking zombies. These parasites are able to completely change hosts' behaviour, making them into more bold creatures. Less kind parasites can take away animals' ability to move, allowing the parasite to remote control the host. Much of these parasites operate on smaller organisms, like insects, but it is possible they could expand to humans. The toxoplasma-gondi parasite has been known to infect rodents, cats, and even humans.. While research on the matter of human brain parasites is in its formative stages, it is still frightening!