Science Daily says that a woman from Nebraska discovered parasites in her eye while vacationing in California. She felt irritation in her right eye, so she flushed it with water and discovered a worm that was about ½ inch long coming out of her eye. She then found another similar worm coming out of her eye. A doctor retrieved a third parasite from her eye. The parasite was sent to the CDC lab and was diagnosed as Thelazia, which usually infects cattle and can be carried by certain types of flies that feed on eye secretions on cattle. No one is sure how the woman became infected, but she is a trail runner and ran into a swarm of flies on a California trail in the Carmel Valley and she had to swat them off. She may have even ingested some of them. After going home to Nebraska, she removed another worm from her eye and continued flushing her eye and using antibiotics to prevent infection.
Another case of this parasite on the west coast occurred 2 years previously so there is some concern that the parasite Thelazia could become a future problem in humans in the U.S. However, I am surprised there are not more reports already if that is the case as many ranchers and dairymen are in close contact with cattle and flies constantly, and for only two cases to develop at this point is unusual. The species of worm has been known to infect cattle since the 1940s, but we are just now seeing it in the human population. The scientists found eggs developing in the worms while in the humans, so it seems that humans are a suitable host for the parasite to reproduce. Hopefully, this is a rare disease and the parasite and infection in humans will remain a rare finding.