The 10 Most Awesome Parasites (That You Don't Want)

It's time for a parasitism party! Like the VH1 Top 20 Video Countdown, only kind of more disgusting. Mira Grant, author of Parasite and the bestselling Newsflesh trilogy, presents the Top 10 Parasite Countdown! Remember, parasites are a vital part of the ecosystem, and should be treated with respect...generally from a safe distance. Some parasites have no effect on humans. Others can kill you. With AWESOME.

10. Toxoplasma gondii: Ever wonder why you like cats so much as an adult when you hated the arrogant little murder-centric jerks when you were a kid?

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Well, the answer may dwell in a tiny little parasite known as Toxoplasma gondii, or toxo for short. Toxo likes to live in rats, mice, and cats, but sometimes finds its way into the brains of humans, where it brings about permanent, irreversible personality changes...including a tropism toward cuddling with kitties. In mice and rats, this leads to disembowelment and consumption, putting the toxo right into the belly of the beast, where it most wants to be. In humans, it leads to spending too much money on catnip and feather ticklers.

(I'd love to see a study of people obsessed with keeping lions and tigers as pets, and what their toxo infection rates are. Maybe the parasite is trying harder than ever to find its way home...)

Regardless of how you may feel about a tiny parasite industriously rewiring your brain, toxo is relatively harmless in healthy adults. It's a different story with sick or immunocompromised individuals, and pregnant women especially should take steps to avoid infection.

Anybody want a kitten?

9. Cymothoa exigua: better known as the tongue-eating isopod or tongue-eating louse.

Wikipedia / Via en.wikipedia.org

Cymothoa exigua is essentially a giant sea-dwelling roly-poly that has dealt with the existential terror of being a tiny, flat, largely defenseless creature living in the big blue sea by turning into a parasitic horror straight out of your worst nightmares.

Instead of chilling with the other isopods, it parasitizes innocent fish (frequently fish of species that are voluntarily eaten by humans; say it with me now, yum!) and replaces their tongues. Don't worry about the poor mute fish, though: once the isopod has moved into place, it stays with the fish for the rest of its life, functionally becoming their tongues.

Yeah. This really happens. This is a real thing that actually happens in the real world, because Nature is weirder and more disturbing than anything you'll ever find in fiction.

Isopods are basically harmless to humans, assuming they never mutate to gargantuan sizes and start feeling on the blood of mammals, which you must admit seems upsettingly plausible when you're looking at these freaky little assholes. Some people even eat them, presumably so they can get early revenge for the inevitable isopod uprising.

And people wonder why I don't eat sushi.

8. Mistletoe: Chestnuts roasting on an open fire...parasitic foliage hanging from the eaves...wait, what?

Wikipedia / Via en.wikipedia.org

Mistletoe is a parasite? Surprise! Mistletoe is what we call a "hemiparasite," a plant that depends on other plants to survive, is parasitic under normal circumstances, but can do some of its own photosynthesis. So it's not necessarily a death sentence for that big oak where you harvest your kissing weed every December; it's just sapping water and some nutrients from your favorite tree, gradually urging it toward that big Home and Garden Shop in the sky. This is why you never see a "mistletoe tree," but instead find mistletoe growing from other plants around the neighborhood.

All known species of mistletoe are parasitic, and being a macroparasite (a parasite you can see with the naked eye), it has been accepted into myth and folklore as a totally normal thing. Imagine hanging tapeworms from your ceiling, and trying to kiss your sweetheart under those. Not nearly as appealing, huh? But they share a lot of similarities, including their inability to take care of themselves.

Ironically, mistletoe is also extremely important to the ecosystem where it grows, and will feed and nuture dozens of other species before it manages to murder that tree. So it serves a real purpose, and should probably be left where it is. Just remember, come the holidays, just what you're kissing underneath.

7. Trematodes: Do you enjoy belonging to a species that reproduces via sexual contact, rather than spontaneously self-impregnating with virtual clones?

Wikipedia / Via en.wikipedia.org

Are you fond of the biological distinction between sexes? Well, you can thank the trematodes for all those squishy, squelchy bits, progenitors of a million love songs and porn films. (Alternately, if you really wish we were a species of parthenogenic hermaphrodites, you can blame the trematodes. They probably aren't going to notice either way, seeing as how they're tiny intestinal parasites that specialize in infecting invertebrates.)

Trematodes, often referred to as "flukes," are largely considered to be the reason that the world evolved gendered reproduction. In a parthenogenic population, flukes can wipe out huge numbers, because no one has a chance to roll the genetic dice and try for a combination that is more resistant to catastrophic parasitic accumulation. In a population which reproduces sexually, lines arise which can resist infection, at least long enough to mature, breed, and roll the dice again. So...yeah. Whether you like sex or wish the whole messy business had never been invented, the odds are good that you can blame it on the trematodes.

6. Dermatobia hominis: Botfly! Human botfly! It's that thing you wish you could unsee! Botfly! Human botfly! Makes you scream "what's that inside of me?!"

Via stream1.gifsoup.com

Ah, Dermatobia hominis, the human botfly. There are many species of botfly, but only Dermatobia hominis parasitizes humans, making it our special, horrifying friend. (As a note to those of you with weak stomachs: you may be tempted to go to YouTube and type in the words "botfly larva extraction." Don't. I mean it. I find the videos which will pop up charming, even soothing, but you may throw up on your keyboard, and I'm not paying for that. If what I have just written sounds fascinating, go ahead and run the search. You may or may not be glad that you did, but you'll have knowledge, and knowledge is power. Disgusting, disgusting power.)

I...look, I can't really find anything nice to say about this little bastards, apart from "neat." They probably serve an ecological purpose, but damned if I know what it is. Mostly, they just sort of bumble around being horrifying and infecting people with their terrible young. Not good neighbors. Do not want.

5. Ascaris lumbricoides: This parasitic nematode is horrible and bad and part of why we really need things like the World Health Organization. I can find nothing good to say about this parasite.

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Its ability to survive earns it a place on this list, but wow do I wish we had a way to make it stop. Let's talk about something more pleasant.

4. Cuculus canorus: The common cuckoo practices species-wide kleptoparasitism, or "brood parasitism," which is neat in and of itself.

Wikipedia / Via en.wikipedia.org

Female cuckoos lay their eggs in the nests of other birds and then fuck off, leaving all the difficult work of child rearing to the deeply confused birds that they have chosen to so accost.

In a beautiful example of nature over nurture, the baby cuckoos will never think "oh, hey, I'm really a reed warbler," fall in love with a nice warbler boy, settle down, and raise hybrid children. Instead, one day, they wake up, go "wait, hang on, I'M A GODDAMN CUCKOO" and flap gleefully into the rising sun, presumably after setting the nest on fire, because YOLO.

What makes the common cuckoo even more fascinating, though, is that while the species goes after a bunch of different birds, each female will specialize in a different sort of warbler or sparrow or whatever. She will pursue those nests above all others, and her eggs will have the best chance of blending in with those broods. Why? How the hell does the cuckoo know? And does she ever think about her unwitting adoptive parents and feel a little bad, maybe wishing she'd been nicer before she burned her childhood home to the ground?

3. Sacculina carcini: Who wants parasitic barnacles? Not crabs!

Wikipedia / Via en.wikipedia.org

Sacculina carcini is a parasitic castrator of crabs, redirecting all that pesky sexual behavior into the deep, abiding need to nurture and protect the sacculina young. So, uh...thanks, flukes, for giving us sexual dimorphism.

That's working out great.

2. Tarantula hawk: If you don't like spiders, this giant stinging insect is your best friend.

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The tarantula hawk is a parasitoid, like our friend the botfly: it implants its eggs in a paralyzed tarantula, and then the eggs hatch and the larvae eat the hapless spider alive.

If you are a spider, you will have nightmares about these horrible death-bringing terrors tonight.

Pleasant dreams.

1. Tapeworms: No species name, because all tapeworms are best.

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No species name, because all tapeworms are best. Did you know there were different kinds of tapeworm? Oh my lands, yes. Some, like the pork tapeworm that frequently infects humans, will hang out in your digestive system making your life miserable. Others, like the species that tends to infect coyotes, will eat your retinas.

In your eyes.

For more creepy and terror inducing parasites, check out PARASITE by Mira Grant.