Recent studies revealed more than a dozen parasitic worms residing in the eyes of a black bear, reigniting concerns that these minuscule worms could pose a risk to human health, potentially leading to blindness.

The bear was found deceased in rural Pennsylvania last November. Researchers retrieved DNA from the tiny worms, measuring less than 2 centimeters, associating them with Thelaziosis, an “emerging zoonotic disease,” as outlined in their publication.

Caroline Sobotyk, the lead author of the study and assistant professor of clinical parasitology at the University of Pennsylvania, noted that this marked the first detection of the parasite in a wild animal within the U.S.

While these worms have been identified in pets previously, the discovery in a wild bear raises alarms about the potential for the eyeworm to spread across the country.

“This certainly heightens the risk of humans contracting this parasite, along with our pets and other animals,” she mentioned.

The study published in the CDC’s journal, Emerging Infectious Diseases, emphasizes that the worms could be transmitted to humans and domestic animals.

“Transmission would not occur directly from wildlife to humans. However, wildlife could act as a reservoir for indirect infection,” explained Kevin Niedringhaus, an assistant professor of wildlife pathology at the University of Pennsylvania and co-author of the study.

According to the CDC, these worms are transmitted by infected flies, which can pass them to animals and potentially humans when they land near their eyes and consume their tears. In severe cases, this can result in ulcers and even blindness.

“The fly collects the worm’s offspring and can then transfer it to another host, whether it’s an animal or a human,” Niedringhaus elaborated. The flies lay eggs on the host’s face, enabling the worm’s migration to the eye.

First identified in American pets in 2018

The expansive territory occupied by black bears in the U.S. along with their close interactions with humans and pets raises concerns among scientists regarding the potential spread of these worms. The researchers also highlight the risk of infection to endangered and threatened species.

“The impact of these worms on wildlife remains unknown,” Sobotyk mentioned.

The initial case in the U.S. occurred in 2018, when a Labrador retriever was found with the worms. Since then, several cases in American pets, primarily in the Northeast, have been documented. A study published in February noted instances of the worm found in two cats and 11 dogs that had not traveled internationally, leading researchers to conclude “this parasite is emerging in North America.”

“It appears that not just dogs and cats are likely contributing to the parasite’s presence here, but wildlife as well,” Niedringhaus said.

Originally, these worms were identified predominantly in Southeast Asia, and following that, cases began appearing in Europe in the early 1990s, according to an article published in Trends in Parasitology. Niedringhaus notes that human cases have also been recorded in Asia.

Since then, cases have been reported across nearly all European countries. Research suggests that red foxes play a significant role in their transmission.

Sobotyk reassured that severe or fatal health repercussions from these worms are unlikely. They remain localized to the eyes, which means they do not migrate to other parts of the body like internal organs.

“These worms are not fatal,” she stated.

“In the worst-case scenario, they could cause blindness,” she noted, but emphasized that most individuals would seek medical attention before reaching such an extreme situation.

Niedringhaus advised that to keep an eye on the emerging parasite, pet owners should ensure that their pets go for regular medical check-ups and should be vigilant for signs of illness, particularly around the eyes, such as excessive tearing.

“It’s crucial to monitor your pets closely since they are likely the primary carriers of potential infections,” he emphasized.