How Do Animals Become Zombies? – Instant Egghead #26


Scientific American Instant Egghead Zombies don’t just exist
in science fiction movies and music videos. They’re for real and we can find them
all over the animal kingdom. It’s not because animals
have come back from the dead, it’s because parasites have figured out how to control the behavior
of their animal hosts. For example, a parasitic fly lays eggs
in a honey bee’s body. The beset bee leaves the hive one night, then crawls in zombie-like circles
before dying. The fly larvae hatch from the bee’s body
to seek their own victims. Then there’s the parasitic hair worm
that lives inside crickets. Crickets can’t swim but the worm forces
the cricket to jump into water when it’s ready to emerge
and start its next phase of life. And then there’s the fungus
that can infect tropical tree-dwelling ants. When the ants are infected by the fungus, they crawl out to a spot on the tree
where the fungus can thrive. Then the fungus kills the ant
and eats its body from the inside out, sprouting spores from the ant’s head. Other ants pick up these spores;
now they’re doomed as well. So how do these dastardly parasites do it? Scientists think these parasites
can control or mimic molecules in the animals’ brains
that influence behavior. And no, humans are not immune
to getting “zombified” by parasites. Researchers think the protozoan,
Toxoplasma gondii, might actually change
people’s personalities making them more sociable
but also reckless. It’s thought that the parasite
alters hormone levels and boosts dopamine, making us feel good. More than 22% of Americans
might be infected with Toxoplasma gondii which we catch from house cats. For Scientific American’s zombie edition
of Instant Egghead, I’m Katherine Harmon.