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Fleas Are Great! But Watch Out For A Worm That Looks Like Vermicelli

Meet some of the nightmarish parasites that live in London's Natural History Museum. Fortunately, they reside in jars.
Rich Preston for NPR
Meet some of the nightmarish parasites that live in London's Natural History Museum. Fortunately, they reside in jars.

Dr. Tim Littlewood handles more gross and terrifying creatures than just about anyone in London.

And he loves it.

"I'm a parasitologist," he explains, "so I tend to work on things that live inside other animals. And most people think of them as quite gross and revolting. But upon looking at these things and studying them, [I find] they are the most beautiful, spectacular animals you can find."

Although you wouldn't want to get one inside of you.

Littlewood works in London's Natural History Museum, which is a temple to science. The halls are lined with stone arches in amber and blue. Ceilings are vaulted like a cathedral, with sunlight streaming down onto the specimens below.

Littlewood leads us into the museum's depths, where slithery creatures lurk, unseen by tourists.

Our first stop was a plain set of cabinets — buzzing with history. The cabinets were owned by the Rothschild family — as in Baron Rothschild — and he was an avid collector of fleas.

Now fleas may not strike you as the most interesting of parasites, but Littlewood quickly corrects this misapprehension.

"I think they're great," he says. "They're small, they jump enormous heights, they do horrible things to people. What can be more fascinating than that?"

In Littlewood's tour of tiny terrors, we move on to a roundworm known as anisakus simplex. "They look a lot like vermicelli," he says. "A couple of inches long."

And you could run into one at the neighborhood fishmonger. "Now it wouldn't be too unusual for you to take a piece of marine fish that you bought from the market nice and fresh, and you start fileting it and a couple of these things start wriggling out," says Littlewood.

If you cook the fish, you'll be okay.

On the other hand, if you're a sushi fan, be wary. You could ingest one of these roundworms. "It is extremely unpleasant because they burrow inside your flesh, and they like to dig around," Littlewood says.

Fish aren't the only potentially hazardous food.

"When you talk to a parasitologist, I can put you off pretty much any food stuff there is," he says. "We can put you off meat quite easily. But I can also put you off plants."

A parasite known as a liver fluke will "put their larval stages on plant material," Littlewood says. "A classic case is watercress." If you ate watercress that carried liver fluke eggs, "you would have a lovely population of flattened liver flukes."

But you don't have to worry about the fat parasite that looks like a grub. They're known as isopod crustaceans. They have legs and exoskeletons and look like mini-armadillos.

"Inspiration for Hollywood movies I'd say," Littlewood says. Fortunately, they're found in fish, clinging to the tongue, which will begin "to atrophy, degrade and fall apart, but the isopod stays there, so it becomes a functional tongue."

Littlewood pauses to admire the new role: "That's a beautiful adaptation as a parasite."

He shares one last parasitic worm, brought in by a member of the museum staff.

It came up due to "natural processes," says Littlewood. "[The staff member] was alarmed one morning to see something unexpected in his bathroom, and good soul that he was, remembering that this was a biological specimen and shouldn't necessarily be flushed away. he retrieved the specimen and brought it to us."

This is one parasite story with a happy ending, reports Littlewood: "In the case of this particular individual, this singular problem solved itself."

As a footnote, I emailed Littlewood to inquire whether Halloween candy is safe from parasites. Children everywhere will be happy to hear his response: "There should be no parasites in Halloween candy."

Copyright 2021 NPR. To see more, visit https://www.npr.org.

Ari Shapiro has been one of the hosts of All Things Considered, NPR's award-winning afternoon newsmagazine, since 2015. During his first two years on the program, listenership to All Things Considered grew at an unprecedented rate, with more people tuning in during a typical quarter-hour than any other program on the radio.

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