Eye worms once only seen in cows now reported in humans

13 Feb 2018

Image: hispan/Shutterstock

The first human has been infected with eye worms that have only been seen before in cattle, and now they’re spreading.

Those of a squeamish disposition might want to turn away now as scientists from the US Centers for Disease Control and Prevention have reported a worrying first for a parasite transmission between animal and human.

Two studies have published their findings in The American Journal of Tropical Medicine and Hygiene, with one revealing that a woman in the US state of Oregon is the first known instance in the world of a human infection with Thelazia gulosa.

The creature is a type of eye worm found throughout the northern US and southern Canada. Until now, it had only ever been seen in cattle, spread on the tears that lubricate the eyeball.

The study revealed that the woman presented with an eye worm infestation after sensing an irritant in her left eye and, after about a week, a small, translucent worm was removed, followed by 13 more over the next two weeks.

To treat the infestation, the worms – measuring less than half an inch long – are removed via tweezers, or, in the case of treatments in Europe and Asia, with the anti-parasitic drug ivermectin.

“Previously, it was thought that there were only two different species of these eye worms that infected humans worldwide,” said Richard Bradbury, who led one of the studies. “Now, we have to add Thelazia gulosa, a third one to the list.”

Another species spreads

Meanwhile, another species of eye worm – Thelazia callipaeda – is reportedly spreading from Asia to Europe and is also transmitted by a common fruit fly, Phortica variegata.

This type of eye worm has yet to be found on the continent of North America, but separate research has found that it is not impossible for them to become active in fruit flies found there.

This study’s author, Domenico Otranto, said: “We’re not sure of the exact distribution of these fruit flies in North America, but their presence in upstate New York suggests this geographic area is potentially suitable for spreading the eye worms that cause human infections in Europe and Asia.”

12 years ago, this particular spread of eye worm in Europe was predicted from the southern part of the continent northwards based on the same evidence that led to these latest findings in New York.

Colm Gorey was a senior journalist with Silicon Republic