Known for its hiking trails, Carmel Valley is where a Nebraska trail runner spends her winters running the California coast. That is, until she contracted a rare parasitic eye worm in March 2018.

A month before her diagnosis, the 68-year-old woman had rounded a corner of one of those trails and found herself in the middle of a swarm of flies. This is when doctors speculate she was infected with a species of eye worm that typically infects cows and is carried by certain flies, Thelazia gulosa. 

A few weeks later, the woman felt irritation in her right eye, from which she removed two worms. An eye doctor removed a third the next day and sent it to the CDC to confirm the infection. This is only the second reported human case of T. gulosa, occurring within two years of the first.

The trail runner was told to flush her eye with distilled water to remove any remaining worms and apply a topical medication to prevent a bacterial infection. She eventually pulled a fourth and final worm from her eye after it was no longer irritated.

The authors of the Clinical Infectious Diseases case study noted that this finding might be indicative of an emerging zoonotic disease—one that jumps from animals to humans—in the United States. Even though there’s no way to officially track T. gulosa in animals, they questioned whether these infections are becoming more common in domestic cows. This could result in “spillover” events in humans, who we now know are suitable hosts for T. gulosa, as eggs were found in the sample taken from this patient’s eye.