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Real Life Monsters: Six Skin-Crawling Creatures to Avoid

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Blood-sucking, brain-eating, flesh-boring monsters live among us. These six horrifying parasites and diseases in humans actually exist.

Parasites in humans
Ascaris lumbricoides worms passed by a child in Kenya, Africa. CDC. Henry Bishop

Nurture loses out to nature every time. Take, for instance, the microscopic world where small, dangerous, downright creepy organisms find sustenance on the living. Read on, if you dare, for this Halloween’s blood-curdling edition of Outdoor Hazards.

Naegleria flowleri: Brain-eating amoeba

Get your nose plugs. This single-celled organism is actually quite common in warm fresh water. Snorted through the nose, the amoeba makes the short hike to the brain, where, in rare cases, it can cause primary amebic meningoencephalitis (PAM). Results can be fatal.


  • Limit time dunking your head under warm fresh water
  • Wear nose plugs

Candiru: ‘Vampire fish’

Parasites in humans
Candiru “Vampire” Catfish; photo by Dr. Peter Henderson

Think twice before you pee in the jungle. This small, freshwater catfish lives in the Amazon River basin and has a reputed predisposition for ammonia, which humans excrete through urine. You know where this is going.

The story goes that the fish swims up the urethra, where its thin, spiny body lodges and feasts. An Edwardian-era British fish biologist shared that “the only means of preventing it from reaching the bladder is to instantly amputate the penis.”

Fortunately, there has only been one observed candiru attack in 1997, a finding that’s still disputed.


  • Don’t believe everything you read
  • I’m still not peeing in the river

Filarial worm

parasites, worms in humans
Filaria worm; photo by Dr. Lee Moore. CDC

Traveling to the tropics? Take note. The microscopic filarial worm is carried by mosquitoes, where they are eventually transmitted to humans and infect the lymphatic system. Living upwards of seven years, generations of worms can invade the lymph system, potentially causing severe lymphedema in the legs, arms, breasts, and genitals.

Fortunately for travelers, it takes repeated exposure; those on short holiday are unlikely to get long-term damage. 

Human parasites
Elephantiasis of leg due to filariasis. Luzon, Philippines. CDC


  • Sleep under a mosquito net
  • Wear long sleeves and pants
  • Use insect repellant

Toxoplasmosa gondii

This nasty single-celled parasite commonly found in undercooked food and cat feces is the numero uno cause of food-borne illness in the U.S. Over 30 million people carry the critter—fortunately, very few have symptoms. Those infected may report flu-like symptoms, but severe infection can cause brain and eye damage and can reactivate later in life after early exposure.


  • Cook your food, particularly pork, lamb, and venison
  • Wash utensils well after preparing meat
  • Change the cat box daily; use gloves when changing kitty litter
  • Don’t change kitty litter when pregnant
  • Why do you even own a cat?

Guinea worm

Guinea worm parasite
Guinea worm removal; photo by Mary Glenshaw, Ph.D., M.P.H. CDC.

If you ever questioned getting a water purifier, here’s another incentive. Guinea worms are found in sub-Saharan Africa and are transmitted by drinking water contaminated by water fleas that host the worm’s larvae. Once ingested, the larvae hatch, burrow through the digestive tract, and live in your body cavity. Adult worms can grow upwards of 2–3 feet long and as wide as a spaghetti noodle. Yum.

The mature female worm forms a blister, causing a burning sensation under the skin. Water will ease the burn…and invite the worm to burst the skin, spewing millions of new larvae back into the water, starting the cycle all over again.


  • Drink filtered water
  • Flowing water is safer than stagnant water


Don’t forget your bug spray when vacationing south of the border. This creepy screwworm fly hitches its larvae on a blood-sucking host vector (mosquito), where the larvae is injected under the skin. The larvae will grow for several months and crawl out of the skin at night. Though the creep factor is high, the Central and South American fly is mostly harmless.

For some Halloween pre-funk, YouTube botfly removal. Eww! You’re welcome.


  • Sleep under a mosquito net
  • Wear long sleeves and pants
  • Use insect repellant
  • Iron line-dried clothes

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