We have completed maintenance on DiscoverMagazine.com and action may be required on your account. Learn More
Planet Earth

The Biggest Parasite Can Grow up to 30 Feet Long, and Live in Your Stomach

The biggest parasite that infects humans can grow up to 30 feet long, but the deadliest one is small enough to lurk inside a mosquito.

By Avery HurtJan 22, 2024 9:00 AM
Parasites, worms, closeup view, 3D illustration
(Credit: Kateryna Kon/Shutterstock)

Newsletter

Sign up for our email newsletter for the latest science news
 

You might not give them much thought, but parasites are everywhere. Estimates vary, but it’s likely that at least 40 percent of the species on Earth are parasites, and maybe as many as half.

A parasite is an organism that lives on or in another organism and lives at the expense of that organism. In other words, a parasite takes what it needs to survive from its host and gives nothing in return. Well, it can give quite a bit of suffering. 

Not all parasites are deadly and disgusting, but some ghastly examples exist. Brain-eating amoebas, blood flukes, leeches, and the worms that cause lymphatic filariasis, also known as elephantiasis, are all parasites. So are bedbugs and lice. There are many kinds of parasites; some do more damage than others. The really bad ones can be very bad, and the big ones can be astonishing. 

What Is the Worst Parasite?

When it comes to the sheer number of deaths it causes, the worst parasite of them all is Plasmodium falciparum. This is one of five species of plasmodia that cause malaria and the one that does the bulk of the damage. 

Mosquitoes transmit malaria, but the organism that causes the illness is the parasite, which lives inside the host mosquito. According to the World Health Organization (WHO), malaria infects more than 200 million people each year and kills more than 600,000, mostly children under five. 


Read More: Florida Malaria Cases: Why an Outbreak Returned to the U.S.


What Is the Biggest Parasite?

P. falciparum is tiny. But some parasites can grow to be whoppers. The biggest one that infects human hosts is thought to be Diphyllobothrium latum. This parasite can grow up to 30 feet long (at least!). That’s more than four times longer than Shaquille O’Neal is tall. Diphyllobothrium is a tapeworm and can infect (and wiggle around) inside the human intestinal tract. 

You can get other tapeworms from pork or beef, but you get Diphyllobothrium latum when you eat raw or undercooked fish. Unpleasant as the idea of a tapeworm is, the good news is that tapeworms typically don’t cause serious symptoms. On the scale of human harm, Diphyllobothrium is a piker compared to P. falciparum.

Often, the only sign of infection with Diphyllobothrium is seeing bits of the worm in your bowel movement, sometimes squirming around. Not pleasant, for sure, but not a killer, either. While infection with a tapeworm often shows no symptoms, it can cause nausea, diarrhea, abdominal pain, fatigue, weight loss, and vitamin and mineral deficiencies.

In some cases, however, Diphyllobothrium can make you very sick. If the worm gets out of the intestinal tract and into the liver, eyes, or brain, the infection can be life-threatening.

How Do You Get Rid of Tapeworms?

Fortunately, tapeworm infections can be easily treated with oral medications. These work by paralyzing the worm, causing it to let go of its grip on your intestines and pass through your bowels. 

The best way to avoid sharing your body with Diphyllobothrium or other tapeworms is to make sure any meat or fish you eat is thoroughly cooked and to be scrupulous about hygiene. Always wash your hands after handling raw meat or fish. Infection with tapeworms of any kind is rare in the U.S., but be extra careful when traveling in areas where the risk of tapeworm infection is high. If you’ve been thinking about going vegetarian, this might be the motivation you need. 

Should We Protect Parasites?

It may seem strange to say that we need to protect parasites. We’ve been talking about some pretty scary critters. But only about four percent of known parasites infect humans. And those that don’t often play critical roles in ecosystems, keeping populations of other animals in check. That’s why a group of parasite experts has developed a conservation plan for parasites.

So avoid the nasty ones — P. falciparum and D. latum and other harmful parasites — but don’t be too quick to condemn the innocent and even beneficial parasites among us.


Read More: Hidden Epidemic: Tapeworms Living Inside People's Brains


Article Sources

Our writers at Discovermagazine.com use peer-reviewed studies and high quality sources for our articles, and our editors review for accuracy, and trustworthiness. The sources below were used in this article:


Read More: This Terrifyingly Cute Parasite Eats Tongues

1 free article left
Want More? Get unlimited access for as low as $1.99/month

Already a subscriber?

Register or Log In

1 free articleSubscribe
Discover Magazine Logo
Want more?

Keep reading for as low as $1.99!

Subscribe

Already a subscriber?

Register or Log In

More From Discover
Recommendations From Our Store
Shop Now
Stay Curious
Join
Our List

Sign up for our weekly science updates.

 
Subscribe
To The Magazine

Save up to 70% off the cover price when you subscribe to Discover magazine.

Copyright © 2024 Kalmbach Media Co.