The Last Nerds on Earth - Ch1, Pg11TEACHER: Alright, alright, quiet down. Now Annie was actually close, except the relationship between a parasite and its host isn't reciprocal. Parasites benefit at the expense of their host.
TEACHER: Annie, care to try again?
ANNIE: Like leeches?
TEACHER: Exactly. Parasites literally live in their hosts. And use them to reproduce, sometimes in wildly interesting ways. There's actually a parasite that infects ants' brains and takes complete control over them.
ADAM: Like zombies!?
TEACHER: Kinda, yeah. The parasite makes them climb to the top of blades of grass to get eaten by cows. The parasite can then successfully reproduce once inside the cow's stomach.
ADAM: What if they infected a human?
TEACHER: This particular parasite has no effect on humans. But there are behavior-modifying parasites that do. By a show of hands, how many of you own cats?
TEACHER: There's a good chance all of you are already infected.