A 28-year-old woman in northern England felt as if "something was moving" in her right eye. Looking in a mirror, she saw a slender, moving structure beneath its surface. At the emergency department, doctors confirmed it: a live, translucent worm about 28 to 30 millimeters long, or just over an inch, migrating under the conjunctiva, the thin membrane covering the white of the eye.
The parasite was Loa loa, the "African eye worm," which is spread by flies in the forests of West and Central Africa. The unusual part was the timing. She had moved to the United Kingdom from Nigeria four years earlier and had not been back since.
The case, from the Mid Yorkshire Teaching NHS Trust in Wakefield, was published March 12 in Cureus. It came with a complication that shaped everything after the worm came out: shortly afterward, she learned she was about six weeks pregnant.
A Worm That Surfaced Years After Exposure
Loiasis spreads through bites from infected Chrysops flies, sometimes called deer flies. Humans are the only known natural reservoir, and most infected people have no symptoms, according to the Merck Manual's professional entry on loiasis. Others develop itchy, temporary swellings called Calabar swellings or notice an adult worm crossing the eye.
The report's authors note that the eye-worm presentation is well recognized where the parasite is common but rarely seen in countries like the U.K. They attribute the four-year gap to the long lifespan of adult worms. The woman did not recall any Calabar swellings or other earlier symptoms.
Her discomfort was limited to mild soreness. Her vision measured 6/6 in both eyes, the equivalent of 20/20, and her cornea, inner eye and retina were normal. Blood tests showed eosinophilia, a rise in a type of white blood cell often seen with parasitic infections, along with a raised inflammation marker. Filarial antibody testing was strongly positive.
She is not the only person to carry the worm quietly for years after leaving Africa. Doctors in Italy described a 37-year-old man from Cameroon who had lived in Italy for nine years without returning when a parasite was seen migrating through his right eye. In the U.S., University of Iowa ophthalmologists described a 64-year-old Congolese immigrant who filmed a worm writhing beneath the conjunctiva of her left eye about a decade after arriving in the country. The Iowa team estimates that adult worms live at least nine years on average.
Removing the Worm Was the Easy Part
Doctors numbed the eye with drops, made a small opening in the conjunctiva and pulled the worm out intact and still moving. The Hospital for Tropical Diseases in London confirmed it was a male Loa loa. At a one-week follow-up, the eye was healing with no recurrence.
But the visible worm is not the whole infection. Other adult worms can remain elsewhere in the body, and females release microscopic larvae, called microfilariae, into the blood. The authors write that drug treatment is aimed at clearing those remaining adults and larvae.
Doctors drew her blood between 10 a.m. and 2 p.m., when Loa loa larvae circulate at their highest levels, and found none. The authors caution that a negative result does not rule out infection.
A Pregnancy That Put Treatment on Hold
The drug of choice for loiasis is diethylcarbamazine, or DEC, which kills both larvae and adult worms, according to CDC clinical treatment guidance. It requires caution. The risk of fatal encephalopathy, a dangerous brain complication, is tied to the number of larvae in the blood. CDC guidance uses 8,000 microfilariae per milliliter as the key threshold. Above it, specialists may first use albendazole or apheresis, a blood-filtering procedure done at specialized centers, to bring the count down.
Pregnancy added another layer. After discussions with infectious disease and tropical medicine specialists, the team deferred DEC until after delivery, citing limited safety data in pregnancy and the need to carefully measure her larval load first.
The published report does not describe her later course or the outcome of the pregnancy.
What U.S. Patients and Clinicians Should Know
Loiasis is rare in the U.S. and does not spread from person to person. Transmission requires the specific African flies that carry the parasite, so the risk centers on people who have lived in or traveled to affected regions.
Treatment here takes coordination. According to the CDC, DEC is no longer approved by the Food and Drug Administration and cannot be sold in the U.S., so physicians obtain it from the CDC after lab results confirm the infection. The Merck Manual advises clinicians to seek expert help before starting it and to rule out onchocerciasis, or river blindness, because DEC can trigger a severe reaction in people with that infection. The Iowa patient completed a 21-day course obtained through the CDC with no side effects.
Anyone who sees or feels something moving on or under the surface of the eye should seek prompt medical attention rather than try to remove it themselves. People who have lived in or traveled to West or Central Africa should share that history with their clinician, even years later, because it can change what doctors look for. Merck notes that the worm's migration across the eye can be unsettling, but lasting eye damage is uncommon.
This is one patient's case, and it does not signal new transmission outside Africa. What it does show is how an infection picked up years earlier can surface thousands of miles away, and why the worm in the mirror is only part of the problem.
Key Questions Answered
What was found in the woman's eye?
A live male Loa loa worm, about 28 to 30 millimeters long, moving beneath the conjunctiva of her right eye. Doctors removed it intact after numbing the eye with drops.
How could the infection appear four years after she left Nigeria?
Adult Loa loa worms can live in the body for years. The authors attribute the delayed appearance to that long lifespan.
Does removing the worm cure the infection?
Not necessarily. Other adult worms and larvae can remain in the body, which is why specialists typically consider drug treatment after removal.
Why was her treatment delayed?
She was found to be about six weeks pregnant. Specialists deferred the standard drug, diethylcarbamazine, until after delivery because of limited safety data in pregnancy and the need to measure her larval load first.
Can Americans catch loiasis at home?
Loiasis is spread by specific fly species in West and Central Africa, not from person to person. Cases in the U.S. involve people who lived in or traveled to those regions.
Published by Medicaldaily.com
