5 of the Worst Parasites You Can Get—And How to Avoid Them

John Kucharski, USDA // Public Domain
John Kucharski, USDA // Public Domain

No matter who you are, or where you live, you have, at some point in your life, served as the host to a parasite—“any organism that has a relationship with another organism where the first one gets a benefit and the other pays a cost,” Dan Riskin, biologist and expert on the Animal Planet series Monsters Inside Me, tells Mental Floss. “These relationships can be very short—like a mosquito [biting] you and then taking off—or they can last for decades, or your whole life.” 

Ahead of the new season of Monsters Inside Me, which premieres on October 15, we asked Riskin to come up with a list of five parasites you really don’t want to host. When making his picks, Riskin went for the most common and the least common, then filled in with different parasites in between. He wasn’t lacking for creatures to choose from; more than half of the animal kingdom, he says, consists of parasites, which have been “hugely influential in the history of humankind.” Read on to be terrified—and amazed.

1. NEW WORLD SCREWWORM (COCHLIOMYIA HOMINIVORAX)

This nasty little parasite (above) made news in the U.S. last year when it infected a herd of rare Key Deer in the Florida Keys. (That outbreak, thankfully, is over.) These creepy crawlies can infect humans, too—and one such case is featured on the new season of Monsters Inside Me. “This family went to Colombia to volunteer at an orphanage,” Riskin explains. Near the end of the trip, the daughter had gone to a water park and came back with a sore on the side of her head.

“The next day, when they were supposed to fly home, the feces hit the fan,” Riskin says. The sore became incredibly painful and started pussing, and the family had to decide: Should they stay in Colombia or go home? Ultimately, they got on the plane. Once back in the States, they took their daughter to the ER, where she was given a haircut that allowed doctors to see the “mobile larvae,” a.k.a. maggots, in her head.

A female Cochliomyia hominivorax fly had landed on the girl’s head and deposited its eggs in a lesion on her scalp; the eggs soon hatched into nearly 2-centimeter-long maggots that began chomping away. Unlike other parasitic maggots—like botflies, for example—the New World Screwworm does not stay put. These maggots were burrowing into the girl’s skull. “If they hadn’t gotten to it, these things would’ve migrated right down sort of towards her face and out her eyeballs or who knows what,” Riskin says. Thankfully, doctors were able to remove the maggots using a combination of petroleum jelly and bacon therapy (basically, luring the creepy critters out with the smell of bacon and the threat of suffocation).

How to Avoid It: Wearing long pants and long-sleeve shirts, applying DEET-based repellents, and sleeping under a mosquito net are your best methods of defense. If you suspect you might be hosting some screwworms, “seek medical attention immediately,” Riskin advises.

2. MALARIA

The malaria parasite.
iStock

According to the CDC, there were 212 million cases of malaria in 2015; 429,000 deaths were caused by the parasite. “You can get it almost anywhere tropical,” Riskin says. “All it takes is a mosquito bite.”

Mosquitos don’t hatch carrying malaria; the bugs pick it up from an infected person. Once inside the mosquito, the malaria parasite takes up residence in the insect’s salivary glands. “When the mosquito bites somebody else, it squirts a little bit of spit into them to help keep the blood flowing—that’s what causes an itching mosquito bite; it’s a reaction to that spit—but they can also be spitting these parasites into the next person,” Riskin says.

In humans, the parasites hang out in cells in the liver, then make their way to red blood cells, which they make explode, spreading more parasites that invade more blood cells. Anyone can get malaria, and people who contract it will experience fever and chills. “It just wreaks havoc on your body,” Riskin says.

The disease is potentially fatal; those who contract malaria and survive might relapse because some species of the parasite can lie dormant in the liver.

How to Avoid It: If you’re going to a country with malaria, consider taking preventative drugs. Otherwise, wear long pants and long sleeves, use DEET-based insect repellents, and sleep under a mosquito net when traveling in the tropics.

3. BRAIN-EATING AMOEBA (NAEGLERIA FOWLERI)

Technically, this amoeba—which can be found in warm, untreated fresh water—isn’t a parasite. “Normally, it’s totally harmless, doing its own thing in the mud, eating whatever it finds there, going about its business, not bugging anybody,” Riskin says. That all changes when a person goes water skiing and gets water harboring N. fowleri violently shoved up their nose.

Now in a new environment, the amoeba resumes eating whatever it can find in the nose. “It makes its way up that olfactory nerve, reproducing and eating, until it hits the brain,” Riskin says. “And once it’s in the brain, it’s game over for the kid that had it shoved up his nose.”

Typically, a victim will begin to show symptoms—which include fever, headache, and vomiting—around five days after infection (although symptoms can appear as early as one day after infection or as late as nine), and will usually die about five days after that. The death rate associated with infection by N. fowleri in the U.S. is 97.2 percent.

That said, getting a brain-eating amoeba is very, very rare: There were 40 infections reported in the U.S. from 2007 to 2016, a rate of four cases per year. (The CDC reports that “36 people were infected by recreational water, 3 people were infected after performing nasal irrigation using contaminated tap water, and 1 person was infected by contaminated tap water used on a backyard slip-n-slide.”) That gives you odds of about 1 in 70 million of contracting a brain-eating amoeba.

How to Avoid It: Basically, just keep water from slamming up your nose. If you plan on engaging in an activity like water skiing during the summer months, “you could wear a nose plug,” Riskin says. “But this is so rare, that might be overkill.”

4. LUNG FLUKES A.K.A. PARAGONIMUS

An adult Paragonimus westermani lung fluke.
CDC, Wikimedia Commons // Public Domain

Humans may find themselves hosting these coffee bean-sized parasites if they’ve eaten raw or undercooked shellfish. As the crab gets digested, the lung fluke larvae are released, and they “move through your body and go all over the place,” Riskin says. Typically, they tear through the abdominal wall and diaphragm to get into the lungs.

People infected with lung flukes may experience abdominal pain and a fever; eventually, they’ll begin to cough up blood laden with eggs. The blood is either spat out or swallowed, allowing eggs to pass in the stool (and, if a host is in water while defecating, the life cycle will continue).

“Our bodies are built to protect us from the environment,” Riskin says, but eating makes us vulnerable. “It’s like if you had a fortress with big stone walls all around it—you still have to get food to the people who live in the fortress. And so, every once in a while, you have to open the gate and let all these ox carts come in and then close the gate. And then, you’ve got to hope that there’s no Trojan horse.”

Untreated, lung flukes can live in the body for 20 years, according to the CDC. Thankfully, once an infection is identified, medication can wipe the infection out.

How to Avoid It: This one’s easy—just don’t eat raw or undercooked shellfish.

5. ELEPHANTIASIS A.K.A. LYMPHATIC FILARIASIS

An elderly man suffering from elephantiasis; one of his legs is much bigger than the other.
NOAH SEELAM/AFP/Getty Images

This condition is caused by several species of roundworms; like malaria, these roundworms thrive in the tropics and are transmitted by mosquito. Once in your body, the roundworms set up shop in your lymphatic vessels—small, one-way tubes in your body that drain liquid away from tissues—and can live there for decades. “They’re cloaked like a Klingon bird of prey,” Riskin says. “The immune system doesn’t even know they’re there.” At least, not until the worms die.

“Once they’re dead, the cloaking mechanism doesn’t work anymore,” Riskin explains. Then your body’s like, ‘Whoa, we’ve got an invader.’” Your body sends white blood cells to the site where the bodies of the roundworms have piled up. The problem is, their bodies have clogged the very vessels meant to drain the liquid away, causing limbs to swell. “It gets more swollen, and the body sends more fluid, and that area gets puffier,” Riskin says. “This just keeps happening, and there’s no way to drain. The draining system is busted.”

The parasite infected 120 million people in 2000, according to the World Health Organization; 40 million people were disfigured and incapacitated by it. While medications have little effect on adult roundworms, there are drugs to help and prevent transmissions to others: In 2015, the scientists who developed a treatment that could prevent infections for around a year won the Nobel Prize for Medicine (alongside another researcher who developed a novel malaria therapy).

How to Avoid It: This mainly affects people in Africa and Asia, so if you’re traveling there, wear long-sleeve shirts and pants, liberally apply insect repellent, and sleep under a mosquito net.

A new season of Monsters Inside Me begins October 15 at 9 p.m. EST on Animal Planet.

20 Freaky Facts About the Giant Squid

Canadian Illustrated News, Wikimedia Commons // Public Domain
Canadian Illustrated News, Wikimedia Commons // Public Domain

Last week, scientists aboard a NOAA Ocean Exploration and Research ship in the Gulf of Mexico captured video of an elusive giant squid—the first recorded sighting in U.S. waters. In the 28-second clip, the cephalopod emerges from the blackness of the deep sea and attacks an electronic jellyfish. After wrapping its tentacles around the luminescent bait, the squid loses interest and disappears in the murk. Since ancient times, philosophers and naturalists have puzzled over this rarely seen enigma. There’s plenty we still don’t know about giant squid, but we’ve learned a lot over the past 20 years.

1. Giant squid eyes are the size of Frisbees.

Woman next to a preserved giant squid eye
Smithsonian Institution, Wikimedia Commons // Public Domain

A staggering 10.5 inches across, a squid’s eyeballs lack the jelly-like substance that gives ours their shape. Instead, they’re filled with water, which leaks out once the invertebrate dies. "The eyes collapse. It's like a collapsed plastic bag,” biologist Dan-Eric Nilsson told NPR in 2012.

2. Female giant squid are bigger than males.

On average, female giant squid are around twice the size of males from the tip of their beaks to the ends of their two longest tentacles.

3. Giant squid suckers can leave ugly battle scars.

The giant squid's main enemy is the sperm whale. While under attack, the squid often retaliate by inflicting large, circular wounds, courtesy of the serrated rings around each sucker.

4.The giant squid’s maximum length is about 43 feet.

At least, that’s what the available evidence tells us. Reports of 60- and 70-footers have never been verified scientifically.

5. Instead of a proper tongue, they use a radula.

This organ rests inside their beaks and is covered with seven rows of denticles—sharp, toothy, backwards-pointing protrusions.

6. There may be just one known species.

A genetic analysis in 2013 suggested that Architeuthis duxis the only species of giant squid, as revealed by a comparison of 43 specimens from around the world. The giant squid gene pool seemed abnormally shallow—all 43 subjects were pretty much indistinguishable in this regard. “It’s completely bizarre,” geneticist Thomas Gilbert said. “How can something be global but have so little variation?” Other researchers, however, argue that there may be as many as eight Architeuthis species out there.

7. Giant squid tentacles can regenerate.

One giant squid corpse found in Canada in 1968 had a partially regenerated tentacle. According to a study of the specimen in the Canadian Journal of Zoology, "the regenerated club differed in length and width, and in the size and pattern of suckers, when compared with the normal tentacular arm." Many cephalopods besides squid are capable of this feat, including octopuses.

8. An estimated 4.3 to 131 million get eaten by sperm whales each year.

The squid regularly show up inside sperm whale stomachs. Approximately 360,000 of these mammals swim the oceans. So, if every sperm whale on Earth devoured an average of one giant squid per month, that means 4.3 million would be offed annually.

But some experts think this figure is way too low. Every single day, male whales put away 300 to 400 squid of various species, while females consume an outrageous 700 to 800 squid. Should Architeuthis represent even 1 percent of their diet, then the whales eat 3.6 million daily. That’s 131 million giant squid killed annually.

9. Giant squid may have helped give rise to sea serpent legends.

In one of Moby-Dick’s more memorable chapters, an Architeuthis slithers towards Captain Ahab’s whaleboat. Apparently, Herman Melville wasn’t a fan—Ishmael describes the squid as a “vast, pulpy mass” complete with “innumerable long arms radiating from its center, curling and twisting like a nest of anacondas.” But Melville wasn't alone. Many believe that this predator’s writhing, snake-like limbs have long inspired sea serpent yarns.

10. 20,000 Leagues Under the Sea grossly overestimates the giant squid’s usual weight.

Jules Verne’s 1869 masterpiece remains impressive today: his novel predicted the invention of both scuba tanks and taser guns. But there are still a few gaffes to be found, particularly during the book’s most iconic scene. When hordes of giant squid attack, the narrator, a French professor named Pierre Arronax, estimates that each one must weigh “between four and five thousand pounds.” But as far as modern scientists can tell, the heaviest animals weigh around a ton—although most are less than 1000 pounds.

11. Like all squids, giant squids have three hearts.

A median heart pumps oxygenated blood throughout the body, which it receives from two smaller ones that pump blood through the gills.

12. Architeuthis penises are about a yard long.

Nobody has ever documented a pair of giant squid getting busy. But biologists suspect that males use their sex organs like syringes, injecting sperm into a female’s skin, where she stores the cells until her eggs need fertilizing. When that happens, the mom-to-be pulls them out of storage (though we’re not sure how).

13. The first giant squid photo ever shot was taken inside of a bathroom.

First photo of a giant squid
Wikimedia Commons // Public Domain

In 1873, Newfoundland minister Moses Harvey acquired a dead Architeuthis which he laid out over his shower curtain rod and preserved for posterity. He’d purchased this specimen for just $10 from a few local fishermen who’d ensnared it with their nets while out in Logy Bay.

14. Giant squid might be cannibals.

Bits and pieces of one Architeuthis showed up in a live giant squid's stomach. But this doesn’t necessarily prove that giant squid dine on one another—some scientists speculate that the squid may have accidentally swallowed a few parts of itself somehow.

15. The Smithsonian has two giant squid on display.

You can see them in the National Museum of Natural History’s Sant Ocean Hall. The pair represents both sexes—here’s a quick look at their 25-foot female (it was probably 36 feet while alive):

16. Their brains are donut-shaped.

But that’s not the weird part. What’s truly bizarre (at least from our mammal-centric perspective) is the fact that its esophagus passes through the hole in the middle of its brain. Giant squids have to be really careful while swallowing, because if a given meal isn’t broken down into small pieces first, it can rub against the brain and cause damage.

17. Before 2004, nobody had ever snapped any pictures of a live one …

History was made by residents of the Ogasawara Islands (located 600 miles south of Japan) on September 30, 2004. Using a line baited with shrimp, zoologist Tsunemi Kubodera and whale-watcher Kyochi Mori attracted an Architeuthis about 2950 feet beneath their vessel. Five hundred still images were then snapped by a submerged camera before the squid took off—leaving behind an 18-foot severed tentacle.

18. … And the world’s first giant squid video didn’t arrive until 2006.

Kubodera would top himself that year when his crew videotaped a young female as they dragged her up to the surface. “We believe this is the first time anyone has successfully filmed a giant squid that was alive,” he said. “Now that we know where to find them, we think we can be more successful at studying them in the future.” Sadly, Kubodera’s prize died during the ordeal.

19. Jellyfish help Architeuthis hunt.

They say the enemy of your enemy is your friend. Certain jellyfish are bioluminescent, which means that they can light themselves up and illuminate the ocean’s inky depths. Predators like giant squid eat many of the fish that hunt jellyfish. So, if a bioluminescent jelly finds itself under attack, it can issue a cry for help by flashing a distress signal, in the hopes that it might attract an even larger carnivore and scare off its assailant. That was the theory behind luring the giant squid with an electronic jellyfish, as seen in the recent NOAA video.

20. It’s not the only monster-sized squid out there.

Meet Mesonychoteuthis hamiltoni, better known as the colossal squid. Though Architeuthis probably exceeds it length-wise, M. hamiltoni is heavier on average, has even bigger eyeballs, and wields swiveling hooks on its tentacles. This isn't a creature you’d want to mess with.

11 Tips for Traveling With Your Pet, According to a Veterinarian

iStock/walik
iStock/walik

Planning a trip can be stressful no matter the circumstances. When you want to include the family pet in your plans, you have a whole new list of things to worry about, including packing the right equipment, checking your hotel’s pet policy, and making sure your pet meets the travel criteria for the state or country you’re visiting. But if you’re aware of the steps you need to take, traveling with your pet can be a positive experience for all involved. Mental Floss spoke with Dr. Danielle Bernal, a veterinarian with Wellness Natural Pet Food, about what to keep in mind before hitting the road with your furry companion.

1. Keep pets comfortable in a travel crate.

You may be tempted to give your pet plenty of room on long car trips, but giving them a confined space that’s their own is usually the better option. According to Bernal, “It’s often better for the dog, because if they’re crate-trained, that’s their area of security.” It’s safer as well: An animal is much better off in a durable crate than it is sliding around untethered in the backseat of a car.

2. Don’t fill your pet's crate with toys.

Giving your pet lots of toys to play with at home is a good thing—but on long car trips it's a different story. Packing every toy your pet loves into their crate takes up what little room they have to themselves. If the crate is too full, it can be impossible for them to move around and adjust their position. “Yes, you want them to be comfortable, but also you don’t want to fill that crate up,” Bernal says. “So almost less is more.”

3. Make sure you have all the correct paperwork.

If you’re planning a long trip with your pet, you won’t get very far without the right paperwork. Many places require incoming pets to have an up-to-date health certificate signed by an accredited veterinarian. Before signing the documents, vets will confirm that your pet is healthy and up-to-date on all vaccinations required by the receiving state or country. If you’re flying, contact the airline to see if any other special paperwork is required to transport your animal.

4. Make it easier to find your pet if they get lost.

An unfamiliar location miles away from home is the worst place to lose your pet. Before your trip, make sure they’re easy to find in case the worst happens. Implanting a microchip under your dog or cat’s skin will make them trackable no matter where in the country they wander off to. If you’re not willing to commit to that procedure, at least make sure the contact information on their tags is up-to-date—that way, they're more likely to be returned to satefy if someone finds them.

5. Skip a meal on travel days.

No matter how accommodating you are to your pet, some anxiety on their part is inevitable. Bernal says a common symptom of this is stress diarrhea—which is the last thing pet owners want to deal with on a long car or plane ride. Even if your pet doesn't seem stressed before the trip, plain old motion sickness can upset your animal’s stomach rather quickly. Bernal recommends feeding them less than you usually would prior to traveling to avoid future accidents: “If you have a pet you know has those sensitivities, I would keep their tummy empty. It will be good for the pet and it will be nicer for everyone in the car too.” That doesn’t mean you should starve your pet if they’re begging for food; just skip the last meal you would normally feed them before beginning your journey.

6. Keep your pet hydrated.

Without regular access to water whenever they need it, pets can get easily dehydrated when traveling. Keep this in mind when traveling and pack extra water for your four-legged passenger. Allowing animals to self-regulate their water intake, perhaps by attaching a bowl to the inside of their crate, is ideal, but if that’s not possible, stop frequently to give them a chance to drink. Another way to keep them feeling good is to feed them wet food instead of dry; according to Bernal, the water content in wet food can help hydrate pets.

7. keep them occupied with a toy.

If you can only give your pet one toy on a long trip, choose something that will keep them busy for as long as possible. Bernal recommends puzzle dog toys like those you’ll find from the pet brand Kong. When your dog is preoccupied on reaching the treat inside the toy, it's harder for them to focus on anything else—including the stress of traveling to a new place.

8. Never leave your pet in a car alone.

Hopefully this is common sense for most pet parents, but Bernal emphasizes that this is the most important thing to remember when traveling with an animal—especially during the summer months. “Don’t leave them in a locked car,” she says. “It takes seven minutes for them to basically move into a situation where it becomes fatal.” It doesn’t matter if you crack a window or if you’re only stepping out of your car for a few minutes. If it’s a hot day, dogs should never be left alone in a vehicle. “We need to make sure that all pet parents are aware of that,” Bernal says.

9. Choose pet-friendly accommodations.

You may love your pet, but that doesn’t mean the owner of the hotel or Airbnb where you’re staying will love them, too; be mindful of this when booking accommodations for your trip. There are plenty of hotels that offer perks for pet owners, like doggie daycare, but even if a place doesn’t advertise their pet policy, it doesn’t hurt to call and ask (or simply confirm what you're reading online so that there are no surprises when you arrive).

10. Make your travel destination feel like home.

Your pet’s crate may not be the best place for all their toys, but that doesn’t mean you shouldn’t pack them when going on vacation. Bringing their favorite items from home can make pets feel more at ease when they arrive at an unfamiliar destination. “Pack things that are familiar to them, so when they arrive at a new spot they’re like: ‘Ok, I feel a lot more comfortable,’” Bernal says. “It helps with their anxiety.” And you shouldn’t stop at toys: Packing their bed, bowl, and blanket can have the same calming effect.

11. Know when it's best to leave your pet at home.

Not every vacation is improved by bringing your pet along. If you plan on spending most of your trip in places that don’t allow animals, like museums, restaurants, and theme parks, it may be best to leave your pet at a kennel or with a sitter or trusted friend. Even if the vacation is pet-friendly, it may not be a good fit for an animal that’s especially anxious. “If you have a nervous dog, he’s actually going to be happier in his home if someone just comes in and feeds him,” Bernal says. Your pet will forgive you for having fun without them.

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