At the entrance of the longest cave in the world, in the state of Kentucky, USA, a national park ranger warns visitors about a fungus inside that is sweeping through bat colonies. However, researchers hope that scientific progress will contribute to stopping this environmental tragedy soon.

These microscopic fungi cause an infection called white-nose syndrome (WNS) that has killed millions of flying mammals since it arrived in the eastern United States nearly 20 years ago, in one of the largest die-offs in modern history.

Despite the lack of a treatment after two decades, scientists have finally started implementing a series of measures to lessen the disease's impact, offering some hope as the fungus begins to spread in the western United States.

Jonathan Richard, a white-nose syndrome specialist at the federal agency responsible for wildlife conservation, says, "We have moved from a situation where we had no idea what was happening to one where we have a set of effective tools for different places and situations."

Among these tools are spraying smoke on animals and caves to slow the growth of fungi or spraying in the summer—outside the bats' hibernation period—with a chemical substance called polyethylene glycol 8000 on the walls.

Michelle Ferrant, a veterinarian at the U.S. National Park Service, explains that other promising solutions, such as the vaccine against this fungal infection, are still under testing.

The expert believes that thanks to "the large number of different tools" used "in the right place and at the right time, we will be able to help a certain number of bats pass the first stage of the disease."

Environmental disaster

This syndrome, named after the white spots it causes around the snout (but also the ears and wings), affects bats in hibernation, waking them up and forcing them to consume their energy reserves.

Researchers recall finding dead bats hanging next to sick ones or crawling on the ground in many American caves.

The first recorded case in Mammoth Cave, Kentucky, dates back to 2013. And since then, the fungus has continued to grow in the pitch darkness and the cold of the tunnel mazes.

Scientists warn that if the disease exclusively affects bats, its implications are much broader than that.

These flying mammals, which feed on insects, play a crucial environmental role. While not all the consequences of white-nose syndrome are yet understood, a study recently published in the prestigious journal "Science" links the significant decline in bat populations in North America to the increased use of pesticides and the rise in infant mortality rates among humans.

Silent tragedy

The United States and Canada are home to more than 40 species of bats; the disease primarily affects those that hibernate.

Evaluating their numbers is extremely complex, but researchers agree that the disease has killed more than 90% of northern long-eared bats, little brown bats, and tricolored bats—the three most affected species.

This last type was widely present in the region. According to researcher and park manager Rick Tumi, the disease also affects Indiana bats in the massive Mammoth Cave.

However, this tragedy passes almost unnoticed. Therefore, many visitors who come to tour the cave are unaware of the existence of this disease.