A 26-year-old woman felt something in her left eye. For days, she couldn’t shake the sensation. But this was no errant eyelash or dive-bombing gnat.
A week after that first irritation, the Oregon resident pulled a translucent worm, about a centimeter long, from her eye. With that harrowing feat, she became the first ever reported case of a human infestation with the cattle eyeworm, Thelazia gulosa. “This is a very rare event and exciting from a parasitological perspective,” says medical parasitologist Richard Bradbury of the U.S. Centers for Disease Control and Prevention in Atlanta. “Perhaps not so exciting if you are the patient.”
Over 20 days, she and her doctors removed 14 worms from her infected eye, researchers report online February 12 in the American Journal of Tropical Medicine and Hygiene. After that, no more irritation.
T. gulosa is a nematode found in North America, Europe, Australia and central Asia. It infects the large, watchful eyes of cattle. The worm spends its larval stage in the abdomen of the aptly named face fly, Musca autumnalis. As the fly feasts on tears and eye secretions, it spreads the nematode larva, which then grow into adult worms.
Two other Thelazia species are known to infect humans, but rarely. There have been more than 160 cases reported for one species in Europe and Asia, and only 10 cases in North America, by a species found in dogs. This new perpetrator was not expected to be seen in a human, Bradbury says.
The young woman had been horseback riding near cattle farms in Gold Beach, Oregon, which may explain her face-to-face with the fly.
“It is just unfortunate for the patient,” Bradbury says, “that she was not able to swish away that one infected fly quickly enough from her eye.”