Thelazia Gulosa: Fourteen Worms Removed From Oregon Woman's Eye in First Human Case of Cattle Infection

Updated | Fourteen worms have been pulled from a woman's eye in the first known human case of an infection normally found in cows.

The translucent parasitic worms—which are spread by flies—measured roughly half an inch in length. Researchers detailed the case in a report in the American Journal of Tropical Medicine and Hygiene.

The 26-year-old-woman was Abby Beckley from Oregon, the Washington Post reported. In the summer of 2016 she had been riding horses in Gold Beach, Oregon, a cattle-farming area. Her left eye became irritated over the following weeks.

After eight days of symptoms she flushed it, expecting to find a rogue eyelash. Instead, she pulled out a worm. "It was alive and squiggling around," she told the Post.

Medical professionals removed more and more worms over the next 20 days, until Beckley's symptoms disappeared. Some of the worms were shipped to a Centers for Disease Control and Prevention laboratory for analysis, where scientists confirmed they were members of the Thelazia gulosa species.

This confirmed Beckley was the first known human host to the cattle infection.

"This patient's outdoor pastimes of riding horses and fishing during the summer months likely allowed exposure to vector face flies," the researchers wrote in the case report. It is likely, they said, Beckley failed to swat away the larvae-carrying flies in time to stop transmission.

Eye worm infections most commonly cause mild local inflammation but, in some cases, they do far more damage. The researchers wrote, "Occasionally, the worms migrate across the surface of the eye and cause corneal scarring, opacity, and blindness."

Other related eye worms have been known to infect humans. The Thelazia callipaeda and Thelazia californiensis species have both been found in human hosts, but are more commonly found in dogs and some other animals. This is only the 11th human eye worm infection reported in the U.S., CNN reports.

"Cases of eye worm parasitic infections are rare in the USA," said Richard Bradbury, the lead author of the study who works with the CDC's Division of Parasitic Diseases and Malaria, in a statement. "Previously, it was thought that there were only two different species of these (Thelazia) eye worms that infected humans worldwide. Now, we have to add Thelazia gulosa, a third one to the list."

This story has been updated to include comment from Richard Bradbury