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Nightmare fuel: Watch this parasite turn normal snails into zombie snails

Meet Leucochloridium paradoxum, a parasite better known as the “zombie snail” worm. This colorful little guy gets into snails, takes control of it, mimics a caterpillar or maggot, and directs the snail to an exposed area so that a bird will eat it.

Yes, this is really a real thing. As biologist Mike Inouye tweeted out earlier this week:

Happy nightmares.

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The life cycle of these things are rather simple. The parasite turns a snail into a zombie snail. The parasite controls the snail, moving it to an exposed area where birds can easily see it. And to top it all off, the worm mimics a tasty treat for birds, and once the bird eats it, the parasite happily reproduces in the bird’s stomach. The bird then poops the parasite out, the snail feasts on the bird’s droppings, and the life cycle repeats itself.

I think this gives new meaning to the phrase “if it’s natural, that means it’s good for you!”

But Leucochloridium paradoxum isn’t the only parasite that can turn its host into a zombie.

Toxoplasma gondii

Toxoplasma gondii is a single-celled parasite most famously known for living inside cats. This parasite has been shown to “increase fearlessness” in rats, as Live Science reports:

Rats infected with the parasite seem to lose their typical fear of cats, and more specifically, their fear of cat urine. A 2011 study in PLOS ONE suggested that infected rats start to feel a type of “sexual attraction” to the smell of cat urine, rather than their usual defensive response to the scent.

And, Toxoplasma gondii can make the jump from cats to humans. There’s some evidence that suggests that in humans, the parasite might contribute to schizophrenia. Live Science continues:

Schizophrenia isn’t the only psychological disorder that is possibly linked to T. gondii. A 2011 study that was done in mice and published in the journal PLOS ONE showed that the parasitemay cause infected brain cells to release high levels of the neurotransmitter dopamine.

Increases in dopamine could play a hand in certain mood disorders, such as bipolar disease, which has been linked to dopamine irregularities, according to the study. Other research done in humans suggests that Toxoplasma could be connected to impulsivity, and even suicide.

The parasite wouldn’t be the first pathogen to alter people’s brain and behavior: The rabies virus, which is deadly in people, has long been shown to have devastating neurological effects.

Not enough to creep you out? Great! We have one more parasite to talk about today.


Ants in the jungle can also be turned into zombies, thanks to a fungus called Cordyceps. Spores of the fungus infect the ant, and once inside the ant’s brain, it makes the ant climb high. As the video below points out, if worker ants see symptoms of this, they carry away the infected ant to die by itself, far away from the colony, because if they don’t, well… Watch what happens.

The fungus grows out of the ant’s head, then explodes, raining down spores on the colony below.

There are actually thousands of species of Codyceps, each specifically adapted for one specific insect.

Happy nightmares!

Cover image via Twitter screenshot

Written by Dan Broadbent

Science Enthusiast. Atheist. Lover of cats.




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