Near Halloween each year, this young girl’s fancies turn to, what else?Zombies! Yes, we all secretly worry about the coming zombie apocalypse, though not enough to assemble the disaster-preparedness kits that we are actually supposed to have. But zombies aren’t real, right? Aside from The Joker’s laughing gas, mass hypnotism, or watching too much Fox TV, there’s no scientific mechanism for turning people into puppets. Or is there? Let’s find out in today’s entry of .

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biomimicry, halloween, zombies, zombie apocalypse, parasites, host-parasite manipulation, crazy cat lady, schizophrenia, Toxoplasmodia gondii, dopamine

It actually turns out many parasites have figured out the art of host mind-control. They set up shop in an unsuspecting host, and force them to do their evil bidding. Which is pretty much just making more parasites. This diabolical possession strategy is straight out of The Exorcist or Rosemary’s Baby. A certain female wasp in Costa Rica, for instance, searches for a specific spider, paralyzes it and lays her egg on it. The larva hatches and feeds on the spider, who doesn’t seem too bothered by it until a couple weeks later, when the larva injects a chemical which makes the spider build a special web. Instead of his usual “bug-catching net,” the spider builds a very strong, rain-resistant hammock, then goes straight to the center to be poisoned and sucked dry. The wasp larva knits herself a tidy cocoon in the hammock, sheltered from the elements, and the adult wasp emerges and flies off to find a new spider. But these are alien arthropods, of course, engaged in an ancient and endless evolutionary war. This stuff doesn’t happen to cute furry mammals and people, does it?

There are many cases of possession among the spineless set. There’s a flukeworm who spends its whole adult life in the liver of a cow. There, it mates and lays eggs, to be shat out by the host. A snail slurps up this flukey delicacy. The eggs hatch, spiral down to its intestines, clone themselves, then float dreamily up to the surface of the snail, to be left behind in a bubbly trail of flukeworm slimeballs. An ant comes along and hoovers up these sweet cystic treats, like an all-girl’s old folks home watching Lawrence Welk. The diabolical flukes set up shop in her brain, then force her to hypnotically ascend a blade of grass and wait, in a bolero-themed trance, to be eaten by another cow. If the ant is still alive at dawn, the flukes release their control and she resumes her ordinary existence, until the next night, when she repeats her somnambulance. She’ll do it every night until her tiny puppet-masters make it back to the mothership.

biomimicry, halloween, zombies, zombie apocalypse, parasites, host-parasite manipulation, crazy cat lady, schizophrenia, Toxoplasmodia gondii, dopamine

But what about sweet little bewhiskered furry zombies? Well, there’s rabies… Remember Old Yeller? Bitten by a rabid wolf, which turned this previously sweet and beloved lab into a frothy mouthed killer. The rabies virus slips slyly from infected saliva to dance among the neurons, turning shy creatures into rage-roids who aggressively savage new victims.

And then there’sToxoplasma gondii. This microscopic one-celled protozoan lives inside our kitty companions. Harmless to them, apparently, but it only reproduces sexually in puddy’s tummy. In between cats, it has to spend its life-cycle inside somebody else, usually cat-feces-snorting rats and cows (bet you didn’t know litter-box snorting was a thing). And while Toxo is slumming it with Ratty, it rewires his brain so that, instead of fleeing from cats, he runs right towards them. This malevolent protozoan goes straight for the primal jugular, disabling the neural circuitry for fear and hijacking the chemistry for lust. Because not only does Toxo assist the cat-rat baton hand-off, it also makes lady rats seriously HOT for infected males. That’s a crafty move for Toxo, because now most of the rat babies will have it too. That’s a brilliant strategy for guaranteeing a round-trip ticket.

biomimicry, halloween, zombies, zombie apocalypse, parasites, host-parasite manipulation, crazy cat lady, schizophrenia, Toxoplasmodia gondii, dopamine

Well, okay, that’s pretty creepy. But human zombies? It’s a stretch. But Toxo is the reason pregnant women aren’t supposed to change cat litter—a fetus can suffer severe brain damage from it. I milked that one for a whole decade (pregnancy, not brain damage). But healthy adults who get it from drinking litter box tea or from liking their meat done rare just get a touch of flu and never know the difference. Toxo cysts lie dormant in over a billion of our brains worldwide, but they don’t seem to do much. Or so we thought. Recently, some interesting studies are showing that people carrying Toxo are a little… well, special. They are about 250% more likely to be in a car crash, for one thing. Could tiny cat-creepers be eating our brains?

It’s bizarre, but this infection comes with a whole suite of sex-specific personality traits. Men with Toxo are more introverted and suspicious. They are risk-takers and rule-breakers. Infected women, on the other hand, are more outgoing and trusting than non-infected women, with more friends. Infected men are more likely to wear wrinkled old clothes, while infected women like the expensive stuff even more than most. And… men with Toxo like the smell of cat pee. Toxo women tolerate the stench even less than uninfected women. And it gets even weirder… women think Toxo men are sexier, and 75% percent of females would rather get to know a guy if he has it. So, I suggest that horny women roll in cat pee (if you’re looking for a serial car accident), and men drink cat litter tea.

biomimicry, halloween, zombies, zombie apocalypse, parasites, host-parasite manipulation, crazy cat lady, schizophrenia, Toxoplasmodia gondii, dopamine

What on earth is going on here? Apparently, Toxo increases the dopamine in our brains, blocking caution and enhancing pleasure. Just FYI, dopamine levels are extra high in schizophrenics, and one-quarter of them have reduced ‘gray matter’ in their brain. This same 25% is also…wait for it… Toxo-positive. We do have effective antipsychotic medicines that help, and when you give these meds to infected rats, they stop running toward cats. Toxo’s association with schizophrenia could be as high as 75%, and infection may be linked to other dopamine disturbances, like OCD, ADHD, and mood disorders. How does the parasite manipulate our feelings of anxiety and pleasure? Maybe we can even borrow their strategy to help people suffering from phobias or PTSD.

The take-home Halloween message here is that the world is full of tiny beasts trying to make it back to their home cat-base so they can have sex. In the meantime, they have hijacked your brain to make you more likely to pass them around. And the crazy-cat lady next door? She wants to eat your brain.

For more on Toxo, read Katherine McAuliffe’s fascinating March 2012 article in : “How Your Cat Is Making You Crazy.” And watch out for zombies!

+ The Biomimicry Manual


An evolutionary biologist, writer, sustainability expert, and passionate biomimicry professional in the Biomimicry 3.8 BPro certification program, Dr. Tamsin Woolley-Barker blogs at BioInspired Ink and serves as Content Developer for the California Association of Museums‘ Green Museums Initiative. She is working on a book about organizational transformation inspired by nature.