Woman jogger gets rare case of parasitic eye worm from flies
Normally spreads through cows, but can live in humans, experts say
The woman had just rounded a corner while running along a steep trail in coastal California in February 2018 when she charged face-first into an unpleasant surprise: a swarm of flies. The pesky bugs quickly engulfed her, forcing her to swat them away from her face and even spit some out of her mouth. But little did she know, things were about to get much worse.
A month later, her right eye started to bother her. She rinsed it with water and out came the source of the irritation — only it wasn’t an errant eyelash or a wayward dust particle.
It was a live worm, roughly half an inch long, transparent and wriggling. And it wasn’t alone.
Soon after the first worm revealed itself, the 68-year-old plucked another one of the squirming critters from her eye, where it had been living in the space between her lower eyelid and eyeball.
In a rare occurrence, of which there is only one other documented case, experts say the Nebraska woman was infected by a parasitic eye worm known as Thelazia gulosa, a species normally found in cattle, according to a recent paper published in the journal Clinical Infectious Diseases. The parasites often spread among cows — their preferred hosts — through certain types of face flies that eat eye secretions, such as tears, the Oct. 22 paper said. The flying insects carry the worm’s young, and when they’re feeding, they expel the larvae onto the surface of the new host’s eye, according to the Centers for Disease Control and Prevention.
The flies the woman ran through were likely larvae carriers, and at least one managed to come in contact with her eyes long enough to leave the parasites behind, Richard S. Bradbury, the paper’s lead author, told Gizmodo. The trail she was running on is located near Carmel Valley, an area southeast of Monterey known for cattle ranching.
Once the woman, who was not named, discovered the two worms in March 2018, she went to an ophthalmologist who extracted a third worm, which was preserved for analysis.
Still, her eye irritation persisted, so when the woman returned to Nebraska, she consulted another doctor. No worms made an appearance during that visit, but the woman was informed that both her eyes were inflamed.
It didn’t take long for the woman to find and pull out what would be the fourth and final worm herself. Her symptoms finally cleared up about two weeks later, the journal article said. Meanwhile, the worm sample was making the rounds. It was first sent to the California State Public Health Laboratory before getting forwarded to the CDC, where researchers nailed down the exact species and noticed a significant detail about the eye worm.
The worm was an adult female and her eggs contained developed larvae, “indicating that humans are suitable hosts for the reproduction of T. gulosa,” the paper said.
The Nebraska woman’s horrific experience was preceded by an eerily similar case involving a 26-year-old woman, who became infected with the worms in 2016 after spending time in cattle fields near her native southern Oregon.
Though there have been only two occurrences of the parasite showing up in humans, researchers say the second case suggests that “this may represent an emerging zoonotic disease in the United States,” according to the October article. “It does raise the possibility that something might have changed in the ecology of T. gulosa in the U.S.A. to cause it to start occasionally infecting humans,” Bradbury told Gizmodo.