Scared of sharks? Stay out of the water. Scared of bears? Stay out of the woods. But parasites? They're small enough to be anywhere. They trigger our natural fear of being preyed on, and add the spice of creeping paranoia.

Parasites can be in the water, or buzzing through the air, or hiding in clothes or bedsheets, or waiting for you inside the body of your loved ones. Even when the parasites are preying on animals - we can't help shuddering with sympathy. Take a look at the ten creepiest parasites in the world.


10. Copepod lives in the eyes of Greenland Sharks

This is a testament to the determination of awful little creatures. Greenland sharks are 18 feet long, and spend 100 percent of their time in water below zero degrees. And they still get eaten by parasites. Copepods lodge in their eyeballs, effectively blinding them, with a long protrusion hanging from the middle of the iris like a string on a balloon. These parasites are so common that it's rarer to find a Greenland shark without them than with them.

9. Lungworm goes through a lot of creatures to get to you

Lungworm is something caught from eating raw fruits and vegetables that haven't been properly washed. It's actually called the rat lungworm - because that's where it starts. Once the rat excretes it, slugs and snails chomp up the rat feces. They hang out on the whirled leaves of lettuce or in the nooks and crannies of fruit, and people eat them. Lungworm doesn't do serious damage - but it does psychologically let you know that you just ate rat feces inside a live slug.


8. Trichomonas gallinae took down T-Rexes

The best-preserved T-Rex skeleton today has holes in its jaw. Some believe these were caused by fights with other dinosaurs, or by accidents. Others believe that they were caused by Trichomonas gallinae, a parasite that infects birds today. It makes the mouth and throat so painful that an animal stops eating and loses bone density.


7. Toxoplasma gondii makes cat people

Not literal cat people, but people who like cats. Let's face it, cats aren't nice. They aren't full of enthusiastic love like dogs. They aren't particularly useful. They ignore people, demand food, and claw people when they don't get food soon enough. And yet - people love them. And it could be because of Toxoplasma gondii. This parasite, found in cats, has infected half the planet. Studies indicate that women who have it tend to be more outgoing and warm, while men tend to be more home bodies. One theory is, it causes people, men and women, to like cats - thereby ensuring that it not only has a well-fed home, but plenty of access to more people.

6. Toxoplasma gondii is on here again for making rats commit suicide

Oh, but Toxoplasma gondii doesn't just affect people. It also affects rats. In fact, it often will start out in a rat. Yes, it's not a perfect home, but rats are survivors, and they're a cozy little place for a parasite. But they're not enough for this one. This one wants to work its way up to cats, and eventually humans. So it moves on up by making rats irresistably attracted to cat pee. The more the rat hangs around places that cats like to pee, the more likely it will be eaten by one of those cats. So Toxoplasma gondii turns its host into suicidal urine junkies.


5. Leucochloridium paradoxum is an eyeball stretcher

Leucochloridium paradoxum eggs infect snails through bird droppings. (Escargot lovers should note that two items on here point the fact that snails routinely eat the crap of pretty much everything. Just saying.) Once they're in the snail, they mature and need to get back up to a bird. How? They make the snail's eye stalk swell and turn green. Not a plain green - a striped green. It looks a little like a caterpillar. A bird sees this bright green, swoops down, and snatches off the snail's eye stalk to eat. Once the parasite is back in its home, it lays eggs which drop out of the bird's hind end and the life cycle starts over.


4. Ophiocordyceps unilateralis has been killing for millions of years

Ophiocordyceps unilateralis is taken in by ants and grows in their body until it's time to spread its seed. For the seed to spread, it needs to get high up, so it forces the ant to find a leaf and cling to it. The fungus then bursts out of the ant's head and scatters around. It gets worse, though. When the ant makes this grip on the plant, it leaves marks that can be identified - assuming you know what to look for. People have found these marks on old plants. Very old plants. Forty-eight-million-year-old fossilized plants. This is the alien chestburster of the ant world. You have to admire its purity.

3. Naegleria fowleri is a brain worm.

It's a brain worm. I don't think I have to explain why it's bad. We've all seen Wrath of Kahn.


2. Parasitic wasps exist

Wasps are awful creatures. Awful. They don't make honey. They don't make a pleasant sound. They just zoom around and sting people. And when they need to reproduce, things get really bad. Some wasps swoop down and take control of cockroaches. Others take control of ants. Really, any poor working insect will do. They hijack the insect's motor system, drive the insect over to burrow, paralyze it, and lay eggs inside it. The eggs then hatch, and eat the still-paralyzed insect alive. One slight thing the wasps have going for them - they do this to spiders. And when they do it, they make the spider weave a web that best supports the wasp eggs and larvae before they kill it off. That's like making the thing dig its own grave. Brutal. I'd feel bad - except it's happening to spiders.


1. Mosquitos are the worst thing ever

Kind of a let down, isn't it? There are a lot of gruesome, or sickening, or horrifying creatures on this list. Mosquitos just suck blood. They're just annoying. The problem, they also carry disease. A lot of it. So much that, by some estimates, half the people who have ever lived have been killed by mosquitos. That is a horrifying idea.

Via Elasmo, CBS, National Geographic, ABC, Neatorama, Caltech, and