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- Parasites are organisms that survive
by mooching off 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 hosts to millions of common parasites
every year, but some are incredibly rare.
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The sparganum 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 sparganum.
Though common in animals,
the recorded infection rate in humans
is something like one to two dozen cases per year worldwide.
Maybe because it doesn't always symptoms in its host
depending on where in your body it settles.
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.
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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.
Well, 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.
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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 crawls straight into your brain
through your olfactory nerves, causing a swelling infection
called primary amoebic meningoencephalitis.
At first, this seems like bacterial meningitis,
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 zero to eight cases are reported,
and it's more common here
than anywhere else in the world.
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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 three inches
or eight centimeters in length,
and they want 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 of the fish.
But humans also excrete nitrogen in our urine,
and since candiru don't notice 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 time we have today
to talk about parasites and stuff,
but if you'd like to learn more, check out our article
10 Rare Parasites on HowStuffWorks.com.
And, hey, if you liked this video,
let us know in the comments and hit subscribe
so that you won't miss the next one.
Charming sparga, spar, (speaks gibberish).
This one is...
Pronunciation?
Gna, gna...
Gnathostoma spinigerum.
We can't stop.
We can't stop!
(horns honking)