11 Disturbing Parasites That Will Keep You Up at Night

Parasites drastically impact our world in more ways than one, affecting host populations and even the biodiversity in an area.
Donovan Alexander
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Parasites affect hundreds of millions of people around the world each year, devastating communities on multiple continents. Parasites have a nightmarish reputation because they are usually tiny, and most people do not realize that a parasite has infected them until it's too late. These creepy critters do not just affect humans. Parasites also infect other animals, insects, and plants. And yes, there is a good chance that you have been infected by a parasite at some point.

According to scientists, parasitism is one of the most common "lifestyles" on Earth, with researchers estimating the ratio of free-living to parasitic life at around 60:40. This makes it difficult to avoid. In fact, there are at least 100 parasites that are host-specific to humans alone.

A parasite is an organism that derives its nutrition from another organism, the host, to the detriment of that organism. Parasites need a host in order to grow and multiply, and this relationship usually causes damage to the host.

Parasites can also spread disease, some of which are fatal to the host. In fact, many of the major diseases ravaging tropical areas across the world are a result of parasitic infections. One of the most common parasites, malaria, is said to kill about 1.5–2.7 million people each year, and this number is only expected to rise as the planet warms, creating new breeding grounds for the parasites carrier, the Anopheles mosquito.


The increase of some parasite-related infections can also be attributed to the rapid growth of unplanned cities, which creates additional breeding sites for mosquitoes and parasites or carriers that breed in standing water. Properly tackling parasites is no easy feat. As you probably guessed, today we are going to look at some of the most dangerous and "creepiest" parasites on the planet. Let's get started. 

1. Pinworms: You might have these in your system right now

11 Disturbing Parasites That Will Keep You Up at Night
Source: Healthline

You or a family member might have these in your system right now. Also known as threadworms, pinworms are one of the most common parasitic infections in North America and Oceania. The parasite derives its name from its thin, white appearance. Enterobius vermicularis usually affecting the digestive tract. Threadworms tend to be spread via the fecal-oral route, with children known to be most susceptible to the disease.

So, what kind of problems do these parasites cause? 

Those infected by pinworms tend to display symptoms like severe itching around the anal/rectum, abdominal pain, irritability, nausea, and weight loss, and they can even cause difficulties with urination. The good news is that the parasite is relatively easy to identify, with the help of a medical professional, and they are rarely deadly. Although, it tends to be more than a little traumatizing to see these tiny, wiggling worms emerge from your rectum.

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2. The emerald cockroach wasp: Real-life zombies

11 Disturbing Parasites That Will Keep You Up at Night
Source: Sharadpunita/Wikimedia Commons

A large number of wasp species live as parasites. The Ampulex compressa wasp is one of these, and resembles something out of a horror movie. This very resourceful, emerald-colored wasp hunts cockroaches. When the unfortunate victim is caught, the wasp directly aims her stinger into the roach's brain, disabling the escape reflex. The stunned cockroach is then dragged back to the Ampulex compressa's lair, where the egg of the wasp is laid in the belly of the cockroach. Once the larva egg hatches, it begins to slowly devour the insect from the inside out, until it forms a cocoon and later emerges as a new adult. We warned you. 

3. Tapeworms: A 15-meter worm can live in your body 

11 Disturbing Parasites That Will Keep You Up at Night
Source: CDC/Wikimedia Commons

The tapeworm is one of the more commonly-known parasites on this list, partly for its distinct look and partly for the public's general fascination with this parasite. This segmented worm tends to live in the international tract of animals/livestock and is transmitted when they drink contaminated water.

It is then spread to humans through the consumption of raw or under-cooked meat from infected animals. The parasite survives by attaching itself to the hosts' intestinal tract where it absorbs the nutrients it needs. Left untreated, they can grow to terrifyingly long lengths, from a starting size of just 1/250 of an inch, to as large as 15.23 meters or about 50 feet

Though easily treated, if left untreated, tapeworms can be extremely dangerous. The worm can cause diarrhea, pain, and weight loss. Unchecked, they can eventually block intestinal ducts, causing seizures, muscle, and even eye damage. The tapeworm can also enter other parts of your body, damaging the heart, liver, and brain. A tapeworm infection can usually be treated with a single tablet of prescription medicine called niclosamide or praziquantel. This kills the worm, which then passes out of the body. Although, if some of it remains in your gut, it could regrow.

4. Leucochloridium paradoxum: Zombie eyes

This parasite is known to infect snails, causing a weird phenomenon. Snails are drawn to the parasite's eggs and eat them. The baby parasites then develop in the gastropod's body, filling its eye-stalks with pulsating brood sacs of larvae. The brood sacs pulsate in response to light and prevent the snail from seeing in the dark - forcing them out into the open, where they are easy prey.

To a bird, the pulsating eye-stalks look like a little worm or caterpillar. Once consumed by a bird, the larvae develop into adults in the bird's digestive system. The adults reproduce and lay eggs, which are excreted by the bird. The infected bird droppings are then consumed by snails, completing the parasites' life cycle. 

5. Hookworms: The parasite that penetrates your skin 

11 Disturbing Parasites That Will Keep You Up at Night
Source: PHIL/Wikimedia Commons

The CDC has estimated that more than 576 to 740 million people around the world are infected by hookworms each year.  These are responsible for 62,000 deaths per year. Hookworms live in the small intestines of humans and are excreted in the feces. These parasites tend to flourish in warmer and moist climates, and in areas with poor sanitation. One of the most common ways to get the disease is by walking on the ground barefoot, as hookworms enter the body by "hooking onto the skin," then burrowing into the body and making their way into the small intestine.

Infections are rarely fatal and tend to produce symptoms of abdominal pain, diarrhea, weight loss, lethargy, loss of appetite, anemia, and skin infection. The infection can be easily treated with medication and is sometimes cleared by the body with any treatment. However, infections among children can be especially dangerous, as the parasitic infection can lead to problems with physical and cognitive development.

6. Cordyceps fungi: A parasite that splits your head wide open 

11 Disturbing Parasites That Will Keep You Up at Night
Source: Sergio Claussen/YouTube

This has to be one of the most famous parasites on our list because of all the lore surrounding it, even making its way into pop culture. Cordyceps fungi release their deadly spores into the air, affecting various insects, particularly ants. In fact, ant colonies are so terrified by other infected ants that they cast any ants acting suspiciously out of the colony.

This is because ants that are infected become disoriented and erratic. Once the infection fully takes hold, it forces the ant to climb to a very high place, like a plant stem, and die. The fungus emerges, ripping open the infected host spreading its spores to other potential victims. 

7. The amoeba that eats your brain

You might want to think twice before jumping into a lake after you read this. Usually residing in warm bodies of freshwater, like lakes and rivers, the Naegleria fowleri, or brain-eating amoeba, is an extremely rare but terrifying parasite.

The parasite lives in warm bodies of freshwater, such as lakes, where it dines on bacteria in the sediment. When the sediment is disrupted, the amoeba can get stirred into the water. Swimmers are infected with they inhale the parasite through their nose.

Once in the body, the amoeba moves from the olfactory nerves to the brain. Because the brain does not contain any bacteria for the amoeba to eat, the organism attacks brain cells for nutrients instead. There is no treatment, but the infection is nearly always fatal. Yet, only 146 cases have been reported in the U.S. in the past 50 years.

8. Cymothoa exigua: The tongue-eating parasite 

11 Disturbing Parasites That Will Keep You Up at Night
Source: Curious Jane/YouTube

You might have come across one of these parasites while fishing. The tongue-eating sea louse feeds on its host's body parts, eventually replacing the tongue of the fish. The parasite feeds on the blood from the tongue, until the tongue eventually completely withers away. After it has destroyed the tongue, the parasite feeds on the blood and mucus in the mouth. 

9. Dracunculus: The meter-long dragon worm

11 Disturbing Parasites That Will Keep You Up at Night
Source: CDC/Wikimedia Commons

Those infected by this parasite, also known as the guinea worm, are in for an unpleasant surprise. People tend to acquire this parasite after drinking water containing infected water fleas. Once a human has been infected, the dragon worm grows by feeding off of your body, until finally, a spaghetti-like worm emerges from the skin.

This worm can grow incredible lengths, reaching up to a meter long. Those infected by the parasite tend to find the worm emerging on their hands or feet, and report symptoms of extreme pain and burning sensations. Sadly, there is no treatment for this parasite, but it can be removed from the body once it emerges by slowly winding it around a stick, over a period of weeks.

10. Malaria: One of the most deadly parasites in the world 

11 Disturbing Parasites That Will Keep You Up at Night
Source: HAYKIRDI/iStock

Malaria kills millions of people around the world each year. There are different forms of the mosquito-bourne disease, caused by four different parasites, known as Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale, and Plasmodium malaria. As you know, the parasites start off in mosquitoes and are passed to humans once the victim has been bitten by an infected mosquito. Malaria can also be spread via blood transfusions, organ transplants, and the sharing of contaminated needles. The parasite disease has a long incubation period, taking anywhere from 7 to 30 days before the first symptoms begin to appear. 

Those infected by malaria may experience fever, chills, headache, nausea, vomiting, malaise, and severe sweating, which recedes after six to ten hours. However, in more severe cases, the parasite attacks the body's vital organs, causing severe anemia, loss of consciousness, seizures, coma, and neurological abnormalities. Some forms of the parasite attack the brain directly and are often fatal. Symptoms may also reappear for years. 

Though there is a range of effective treatments, the best defense is to eliminate areas of standing water where mosquitos breed and to not get bit in the first place, using nets around beds, and mosquito repellant.

11. Toxoplasma gondii: The parasite that bends minds to its will 

11 Disturbing Parasites That Will Keep You Up at Night
Source: Wikimedia Commons 

Dubbed the" brain-washing parasite," Toxoplasma gondii has been known to infect rodents in a very peculiar way. This parasite causes mice to lose their sensitivity to cat urine, and to stop avoiding areas with cats. This invariably leads to a cat eating the infected rodent. The parasite then reproduces within the cat, passes out in its feces, and eventually makes its way to the next rodent host.

Toxoplasma is also one of the most common human parasites in developed countries, infecting an estimated 30–50 percent of the global population. In humans, the parasite usually causes no symptoms or very mild, flu-like symptoms, although it may cause very a serious illness, toxoplasmosis, in those with severely weakened immune systems.

Toxoplasma may also cause some humans to slightly alter their behavior, mood, and even their reaction times. Although in humans it is not associated with an increased risk of being eaten by cats.

What do you think about the parasites on this list? 

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