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Parasites aren’t just weird – some of them are downright frightening (and might be living inside you right now).

5 Rare Parasites Found in the Human Body
http://health.howstuffworks.com/diseases-conditions/infectious/5-rare-parasites.htm

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Parasites are organisms that survive by mooching off of a living host body – like yours. From single-celled protozoa that exist harmoniously within us, to fleas that suck our blood, to tapeworms that set up shop in our intestinal tracts, humans play host to millions of common parasites every year. But some are incredibly rare.

The Spargana Worm: Ah yes, it’s hungry for human flesh, can grow to be almost a foot long, and may live for 20 years in your body: charming spargana. Though common in animals, the recorded infection rate in humans is something like 1 to 2 dozen cases per year worldwide. Maybe that’s because it doesn’t always cause symptoms in its host, depending on where in your body it settles down. But if it invades your brain, inner ear, spinal cord, or eyes, it can cause symptoms from headache and vertigo to blindness and paralysis. The moral of the story: Avoid undercooked meat and untreated water. And definitely don’t use raw frog meat in poultices on your wounds or eyes.

The Gnathostoma spinigerum Worm: These critters actually aren’t able to reproduce inside a human body the way they do inside other hosts (like freshwater fish and tasty crustaceans). While that’s good news for you, it’s bad for the parasite. Once you’re infected, they live out their lonely 10-to-12-year life cycle migrating throughout your body, causing swelling under your skin. This condition, gnathostomiasis, has begun emerging outside of its common habitat in the tropics of Asia. Cooking your protein of choice to an internal temperature of at least 145 degrees Fahrenheit [that’s about 63 degrees Celsius] will help keep you safe.

The Naegleria fowleri Amoeba: This single-celled, heat-loving parasite is found in warm freshwater lakes, ponds, rivers, and hot springs. It infects humans by entering through your nose. Then it crawls straight to your brain through your olfactory nerves, causing a swelling infection called primary amebic meningoencephalitis (or PAM). At first this seems like bacterial meningitis (with headaches, nausea, and a stiff neck), but it quickly morphs into something much more serious (think seizures and hallucinations). It can kill you in less than a week. The good news? Of the hundreds of millions of potential exposures every year in the U.S., only 0 to 8 cases are reported – and it’s more common here than anywhere else in the world.

The Candiru Catfish: Wait, catfish? What the stuff? Yes, this tiny Amazon river fish (a relative of the catfish beloved as a food source in the U.S.) is a parasite. They’re usually less than 3 inches or 8 centimeters in length, and they vant to suck your blood. Well, they want to suck fish blood, really, so they’ve adapted a keen nose for nitrogen, which fish excrete through their gills. The candiru senses that nitrogen, gets in through the gills, and feeds off the fish. But humans also excrete nitrogen – in our urine. And since candiru don’t know the difference between a gill and a urethra… well, just remember to use the bathroom before you go swimming in the Amazon river.

And that’s all the parasite stuff we have time for now, but you can learn lots more at HowStuffWorks.com. Like how one parasitic worm prefers making a home in your lungs and how to best wash produce to remove potentially harmful bacteria. And hey, if you liked this video, let us know in the comments and subscribe so you won’t miss the next one.