Parasitic Worms Found in a Woman's Eye—First Case of Its Kind

An Oregon woman’s infection marks the first time on record that an eye worm species normally found in cattle has been seen in humans.

By Erika Engelhaupt
Published 13 Feb 2018, 13:36 GMT
An adult female Thelazia gulosa eye worm is seen just after it was removed from the ...

An adult female Thelazia gulosa eye worm is seen just after it was removed from the patient's eye for analysis.

Photograph by Cdc

Abby Beckley was salmon fishing in Alaska when she felt something in her left eye.

“It felt like when an eyelash is poking you,” she says. But try as she might, the 26-year-old couldn’t find a hair—or anything else—in her eye. The feeling wouldn’t go away, and after about five days, Beckley was frustrated.

“So one morning, I woke up and I was like, If it’s the last thing I do, I’m going to get whatever the heck is in my eye out of there,” Beckley says. She screwed up her courage, pulled back her eyelid, pinched the inflamed skin underneath, and gave it a yank.

When she looked down, she says, “there was a worm on my finger.”

Beckley is now the first person in the world known to have been infected with a particular species of eye worm. Called Thelazia gulosa, the parasitic worm had been seen in cattle eyes—a normal pit stop in its life cycle—but never before in a human’s.

What’s more, hers is only the 11th human case of Thelazia eye worms of any species in recorded U.S. history. The last known case, researchers report today in the American Journal of Tropical Medicine and Hygiene, happened more than 20 years ago.

Show Yourselves

Beckley didn’t know any of that as she stared at the worm on her finger in the summer of 2016. The small, nearly transparent creature wriggled for a few seconds, then died. She had seen similar-looking worms in salmon, so Beckley wondered if she’d somehow accidentally transferred one to her eye. But then more worms started to appear, and it became clear this was a bigger problem.

“I was just pulling them out, so I knew there were a lot,” she says.

Beckley had pulled five more worms from her eye by the time she made it to a doctor in Ketchikan, Alaska. The doctors there were “legitimately freaked out,” Beckley says, but they didn’t know what the worms were or if they were dangerous.

The eye worm Thelazia gulosa can be seen on the surface of the patient’s inner eyelid.

Photograph by Dr. John Hoyt

Worried about the proximity of the creepy-crawlies to her brain, Beckley decided to return to Portland, where her boyfriend’s father, a doctor, prepared the medical staff at Oregon Health & Science University for her arrival.

At the hospital, “they basically rolled out the red carpet,” Beckley says. Doctors and interns gathered, hoping to see the rare eye worms. They seemed a bit sceptical at first, she says, and suggested that maybe what had looked like a worm to her was really just mucus.

But Beckley kept insisting that there were worms in her eye: “I kept thinking, Show yourselves! You have to show yourselves!” she says. For the next half hour, she sat with hospital staff staring into her eye, waiting for a worm to appear.

“I’ll never forget when the doctor and the intern saw it wiggle across my eye,” Beckley says. “He freaked out and jumped back, and was like, Oh my god, I saw it! I just saw it!”

As for Beckley, “she handled it all with remarkable grace and stride, and is incredibly strong,” says Erin Bonura, the infectious disease specialist at OHSU who treated her.

Mystery Worm

Ophthalmologists managed to snag one of the worms from Beckley’s eye, although it broke in half, and they sent the pieces to the U.S. Centres for Disease Control and Prevention (CDC).

That worm and several more pulled from her eye made their way to Richard Bradbury, who leads the CDC’s Parasitology Reference Diagnostic Laboratory, the nation’s primary resource for identifying rare parasites. They analysed nearly 6,700 mystery samples last year alone.

“When you don’t know what it is, it ends up on our table,” Bradbury says.

“All these parasites are rare, and this one is extremely rare,” says of Beckley’s eye worm. He had to dig out a German research paper from 1928 to finally identify the species as Thelazia gulosa, making it the third species of Thelazia to turn up in a human eye, along with a species in Asia and one in California.

The worms are carried by face flies, which feed on the tears of cattle, horses, and dogs; you may have seen them persistently buzzing around an animal’s eyes. If you can get over the horror of eye worms and face flies, they’re a fascinating example of parasite survival.

First of all, Bonura says, eye worms can’t survive without face flies. The worm larvae can mature only inside a face fly’s digestive tract and organs, and then they find their way to the fly’s mouthparts. When the fly lands on an eyeball and begins to drink tears, the late-stage worm larvae climb out of the fly’s proboscis and onto the eye. There, they finish their transformation into adults and produce more larvae, which must get picked up by another face fly—or the worms face death.

In Beckley’s eyes, “there was no way for them to continue their life cycle, so they all just died,” Bonura says. It’s still a mystery exactly how the worms got into Beckley’s eye, but Bonura suspects it may have happened when she passed through cattle pastures.

Could It Happen to You?

In one bit of good news, the worms don’t burrow into the eyeball itself and instead take up residence on the soft tissue under the eyelids and around the eye socket. Once in an eyeball, though, there aren’t many treatment options. Sometimes, anti-parasitic drugs are used to kill them, but these can worsen inflammation.

In Beckley’s case, the best treatment was for her to gently pull them out, one by one. Over the course of 20 days, Beckley pulled 14 worms out of her eye. Still, the doctors involved in the case agree that these eye worms aren’t a looming public health crisis.

“Do not panic that you’re all going to get eye worms,” Bonura says. Not only is it extremely rare for a person to get a face fly in their eye, it’s even more rare for the fly to stick around long enough to deposit worm larvae. The best prevention, Bonura adds, is just to shoo flies away. And if one gets in the eye, remove it right away.

“As long as you’re doing what we would normally do, it should be fine,” she says.

Beckley’s worms didn’t leave any lasting damage, and she says her vision is fine. A year and a half later, she had trouble even remembering which eye the worms had been in.

And in case you’re wondering (I did), she didn’t keep any: “I did not want to spend any more time with those things than I needed to.”


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