Woman Finds Parasitic Worms in Eye After California Run, Scientists Warn It Could Be 'Emerging' Disease in U.S.

Parasites which usually grow in cows infected a woman's eyes after she went for a trail run in California.

The unnamed woman is thought to be the second human to be infected with the parasite known as Thelazia gulosa, or cattle eye worm, according to a case study published in the journal Clinical Infectious Diseases.

Researchers believe the worm is an "emerging" disease in the U.S.

The 68-year-old woman from Nebraska was in the Carmel Valley area of California in March 2018 when she felt something in her right eye.

She washed her eye out with tap water, causing a wriggling roundworm, or nematode, to fall out. The woman inspected her eye and discovered a second worm.

The woman visited an eye doctor in nearby Monterey, who found a third roundworm in her eye, and sent it off the U.S. Centers for Disease Control and Prevention (CDC) for testing.

In case worms remained burrowed in the eye, the doctor advised the patient to regularly wash her eye with distilled water and use a medication to stop bacterial infections.

Back in Nebraska, the woman found a fourth worm in her eye. She continued washing her eye for two weeks, after which point the worms didn't return.

Thelazia gulosa spread when face flies feed on the tears of a host, like a cow, enabling the larvae to crawl out of their mouthpart and on to the eye area. The parasite is found in North America, as well as Asia, Europe, and Australia.

It is unclear how the worms got inside the woman's eye. But doctors suspect she was infected during a trail run in Carmel Valley a month before she found the first worm because she remembered encountering a swarm of flies.

The woman recalled "swatting the flies from her face and spitting them out of her mouth," the case study detailed.

After testing the specimen, the CDC revealed the worm was a cattle eye worm.

The researchers also found eggs in the worm, suggesting the human body is a site where they can reproduce.

As the case is the second in two years, the authors said this suggests the parasite may "represent an emerging zoonotic disease in the United States," meaning one that has spread from animals to humans.

In 2016, Abby Beckley is believed to have become the first person in the U.S. to catch Thelazia gulosa. She told National Geographic last year she was salmon fishing in Alaska when she suddenly felt as if a lash was poking her eye.

After days of discomfort, she pulled at the irritated part of her eye, and out came a worm.

Beckley, who was 26 at the time, removed five worms out of her eye before she visited a doctors' office in Ketchikan, Alaska, where staff were "legitimately freaked out," she said.

She was sent to Oregon Health and Science University, where doctors and interns gathered to see worms.

Eventually it was decided the best course of treatment was for Beckley to simply pull out the worms until they were all gone. She removed 14 over the course of 20 days. Beckley has since fully recovered.

Richard Bradbury, leader of the CDC Parasitology Reference Diagnostic Laboratory, who co-authored the Nebraskan woman's case study, had to look at literature from 1928 to identify the worm as Thelazia gulosa.

Speaking to Newsweek, Sarah Sapp, biologist at the division of Parasitic Diseases and Malaria at the CDC's Center for Global Health, said thatseeing two cases of T. gulosa pop up in a short space of time "is interesting and not only from a 'parasite novelty' standpoint."

The parasite isn't native to North America, but was introduced through flies, she explained. "The fact that we have detected infections in the natural host (cattle), and now in humans, could mean that this formerly exotic parasite has become established enough in nature to spill over into a new host (humans). It serves as an example of how parasites and diseases in general can cross not only geographic borders but host species borders as well."

Sapp stressed the parasite is "relatively benign in humans, so there is no need to panic."

"This is still an exceedingly rare infection in humans, particularly in the United States," she said. "However, because it's so rare, it is difficult to comment on the efficacy of prevention strategies. If someone suspects infection with these eye worms, the person should seek medical attention for appropriate diagnosis and treatment."

This article has been updated with comment from Sarah Sapp.

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A stock image shows a woman running in the countryside. Researchers have described the case of a woman whose eye was infected by a parasite after she went running. Getty