A recent case report highlights a rather unsettling souvenir from a trip to South America; a woman ended up with a worm parasite lodged in her eye. Researchers from Chile and other institutions shared the findings last month in the journal Emerging Infectious Diseases. The 26-year-old woman from the UK experienced a severe case of conjunctivitis, which was traced back to an adult Philophthalmus lacrymosus fluke. She likely contracted it weeks earlier during her visit to the Galápagos Islands in Ecuador. Thankfully, the worm was successfully removed from her eye without complications, but the researchers warn that others in the region might also be at risk from such infections.
“Our clinical and epidemiologic findings show that the zoonotic eye fluke P. lacrymosus can infect humans in South America. The findings also suggest that the parasite might be endemic on the Galápagos Islands in Ecuador,” the researchers noted.
A fluke case
According to the report, the woman sought medical help in Santiago, Chile, nine days after experiencing significant pain, swelling, and the unsettling feeling of something moving in her right eye. Upon examination, doctors identified an “elongated mobile structure” within her conjunctiva, the thin membrane protecting the eye. They managed to remove the foreign object using a moist cotton swab, which alleviated her discomfort. In the days that followed, she fully recovered without any further issues.
Upon microscopic examination, the invader was confirmed as a P. lacrymosus fluke through genetic testing.
Flukes belong to a group of parasitic flatworms known as trematodes, characterized by their complex life cycles involving multiple hosts that can include humans. While infections can occur in various body parts, those affecting the eye are primarily due to Philophthalmus species like P. lacrymosus. Instances of such infections are infrequent, with only 12 documented cases since 1939.
The P. lacrymosus flukes are found in Europe, Asia, and the Americas, primarily maturing in waterbirds and sometimes infecting other vertebrates, including mammals.
A hidden endemic threat?
In this case, the woman had traveled to Chile, Ecuador, and Peru before her symptoms emerged. However, her only exposure to natural water occurred in the Galápagos Islands, making it the likely source of her infection, according to doctors. How exactly this infection was acquired remains unclear. While some reports suggest that swimming in infested waters can lead to infection through direct contact with larval cysts, others indicate that handling contaminated food may also be a risk.
There’s still much to learn about these worms, including how many distinct Philophthalmus species exist globally. Interestingly, the fluke found in her eye resembles a recently identified species, P. zalophi, seen in sea lions near the Galápagos Islands. The similarity raises the possibility that P. lacrymosus and P. zalophi might actually be the same species, as flukes are known to physically adapt to their mammalian hosts, which could have led to misidentifications in the past.
Regardless of the exact number of species, it’s likely that some live in the Galápagos. More research is needed to better understand the ecology and host range of these flukes. While human infections appear to be rare, travelers to potentially affected areas should be mindful of possible eye issues, as should the healthcare professionals tending to them.
“Travelers and physicians should consider philophthalmiasis if someone reports a foreign body sensation during or after travel,” said Thomas Weitzel, the lead author and a tropical medicine and parasitology specialist at Universidad del Desarrollo in Chile. “The worm should be extracted by an ophthalmologist.”
I certainly find it unsettling to think about the various bizarre things that could potentially infest our eyes.
This article has been updated to include comments from the study’s lead author.
