Worms that live in eyes and are transmitted by flies can reach humans, experts fear

The discovery of a dozen parasitic worms in the eyes of a black bear has sent alarm bells ringing. Scientists fear that the tiny worms known for causing blindness can also affect humans in the near future. 

The worms are linked to a zoonotic disease called "Thelaziosis", scientists wrote in a paper. The bear was killed in rural Pennsylvania in November last year. The researchers found the worms in its eyes and extracted DNA from them. The worms are less than two centimetres in length

The researchers say that this is the first time that the parasites have been found in a wild animal in the United States. 

Caroline Sobotyk, the principal author of the study and an assistant professor of clinical parasitology at the University of Pennsylvania, said, "This does increase the risk for us humans to get this parasite as well and for our pets and other animals."

The worms have earlier been found in pets, but the discovery in a wild animal triggers fears that the parasite can spread across the country. 

According to a new research paper published in the Centers for Disease Control and Prevention's Emerging Infectious Diseases journal, there is a risk of "transmission to humans and domestic animals."

Kevin Niedringhaus, co-author of the study, says that it is unlikely to reach humans directly from wild animals.

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"But wildlife could act as what we call a reservoir" from whom an indirect infection might come, he said. Kevin is an assistant professor of wildlife pathology at the University of Pennsylvania.

According to the CDC, flies act as a carrier for the worms that transmit them to animals, including humans. The infected flies land near the eyes, feed on the tears and transmit the worms. Ulcers on the eyes are a common symptom and the worms can also cause blindness.

"Offspring of the worm is probably being collected by the fly, and then that's being carried over to another host, whether it's another animal or a human," Niedringhaus said.

Black bears are widespread in the US and scientists fear that this makes it easier for the parasite to spread. There are also chances that endangered and threatened species might also get infected. 

In the US, the first case was identified in a Labrador retriever in 2018. More cases in pets soon followed. Later, a paper talked about worms in two cats and 11 dogs that had never left America. 

According to an article from the academic journal Trends in Parasitology, the parasite was first globally identified in Southeast Asia in the early 90s and afterwards, cases started to emerge in Europe.