Only for the second time in the medical literature has a human been infected with a rare infection by Thelazia gulosa – an eye parasite that turns the eyes into a place for reproduction of brilliant worms.
While this is only the second documented case in humans, given both known infections within two years of each other, scientists say we could look at the emerging type of zoonotic disease in the United States.
At a startling moment in a case report documenting a second infection, scientists at the CDC's Parasitic Diseases Unit tell the story of a 68-year-old Nebraska patient who spent her winters in the warmer climate of the Carmel Valley in California.
During these visits, she enjoyed the trail running she did one day in early February 201
"He remembers having flies from his face and spitting them out of his mouth," the researchers explain in their report.  The strange episode, however, does not end; in fact, it may have just begun.
The next month, the woman noticed an irritation in her right eye and the cause of the discomfort did not take long to unravel.
While washing her eye with tap water, she washes a transparent, moving round worm about half an inch in length (about 1.25 cm).
She was not alone. Further examination revealed another worm in her eye (which she also managed to retrieve) and the next day visited an ophthalmologist who removed a third and prescribed an antibiotic ointment to treat any bacterial infection.
A few weeks later, she returned home to Nebraska, still experiencing ongoing irritation and a "foreign body sensation" in both eyes. Another ophthalmologic examination diagnosed her with mild bilateral papillary conjunctivitis, but failed to detect additional nematodes.
However, the patient found and removed a fourth worm from his eye shortly thereafter and fortunately his conjunctivitis subsequently resolved.
This fourth worm is the last one ever found in a woman's eyes, and for that she may consider herself lucky. At least in the only previous case of a person with the same infection, 14 worms were found, stinging in the eyes of a 26-year-old patient.
Analysis of a nematode sample collected by a Nebraska patient confirmed that her case was the second known case of the parasite T.
"The worm was identified as an elderly woman T. gulosa "the authors write.  "The important thing is that eggs containing developed larvae have been observed in the uterus indicating that humans are suitable hosts for reproduction of T. Gulosa ."
Other species Thelazia The species were known to infect humans before in the United States, causing telaziasis, although documented cases are rare.
However, if you have these worms that roll in your eyes, however, you do not want to delay in removing them, the researchers warn.
"In long-term untreated infections, chronic irritation caused by the passage of adult worms through the cornea can lead to keratitis, loss of visual acuity or even blindness," the team explains.
"In reported cases where infected nematodes have been removed from the eyes within one to two months of the first observation, the associated conjunctivitis has resolved and no long-term clinical effects have been observed."
In such cases, it is relatively impossible to determine for sure just how the patient got infected, but in both cases with humans, the probable cause is known.
Thelazia's eyes are transmitted between animals by species of flies. Most often in the case of T. gulosa they are known to transmit the infection to cattle.
As such, if you are close to cattle (such as the patient who visits the farm in the first case who practiced horseback riding) or you have the misfortune of encountering a person first in a swarm of flies in a rural area (such as the second patient), you just might have a chance to infect the parasite.
How significant is the threat? From what we know so far, the incidence of these infections in humans remains extremely rare, although the temporary coincidence of these two cases can be significant.
In cattle, T. gulosa infections have been reported in several US states, as well as in Canada, Europe, Asia and Australia, but parasite testing in these regions may not be considered a strict priority. .
"The causes of this species only now infected people remain unclear," the authors explain.
"The monitoring of telazyase in cattle is not monitored and therefore it cannot be determined whether there is an increasing spread of T. Gulosa infections in domestic bovine animals leading to zoonotic events of human transfusion and other unusual hosts. Updated surveillance studies on domestic and wild ruminants would help to better clarify the situation in these hosts and indicate in which regions of the United States other human infections may occur.
Findings were reported in
Cly night infectious diseases .