For Devastating Bat Fungus, Potential Treatments But No Easy Solution

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A bat that was netted at Pinnacles National Monument on the night of July 10, 2019. As part of the effort to respond to the presence of a deadly fungus found in four California bats, scientists are attaching radio transmitters to members of different species to discover where they hibernate. (Lindsey Moore/KQED)

Last week, state scientists announced they had discovered for the first time in California an invasive fungus that causes a disease responsible for the death of over 6 million North American bats.

The cold-thriving fungus, Pseudogymnoascus destructans, was found in samples collected from four little brown bats, which is the name of the species, in Plumas County near Lassen Volcanic National Park.

Scott Osborn, a senior environmental scientist with the California Department of Fish and Wildlife, is leading a multiagency effort to detect and contain the disease, called white-nose syndrome.

But he says eradication isn’t an option yet, and there is no one solution to protect bats scattered across Northern California.

The fungus is here and it's more than likely going to spread,” Osborn said. “It's our ardent wish to minimize the impact of the disease. But at this point, I can't say that we're going to really try to prevent it from occurring. I don’t think we can claim to have the power to do that.”


While the fungus was detected in low levels in the California bats, that is often the first indication they will contract the disease.

“The early signs of the fungus showing up is a clear harbinger of doom,” said Winifred Frick, a chief scientist with Bat Conservation International. 

According to a study Frick led of the disease’s progression in bat colonies in the Northeast, entire roosts of little brown bats became infected within two years of the fungus’ detection. 

“In those situations, anything you could do to buy more time or potentially allow species to persist on the landscape, even if it is at a small subset of sites where they used to occur, that’s prevention of a species extinction, and in my view is worth it,” Frick said.

White-nose syndrome, so-called because of the discoloration the fungus causes on bats’ noses, was first discovered in New York in 2006. The fungus eats away at their skin and causes lesions, awakening the animals from their winter hibernation. Fastidious groomers, afflicted bats consume all of their fat stores by cleaning themselves, depleting them of needed energy. 

In the Northeast, thousands of dead bats have been found in and around caves and mines, the disease wiping out virtually whole colonies in some areas. 

Osborn’s team is expanding bat surveillance, especially in the Sierra Nevada and other high-elevation places in Northern California that experience cold winters. With an accurate count of bats, researchers can identify if the population dips, a sign that the disease has begun its onslaught.

While bats in the northeast roost in large colonies of thousands or tens of thousands, Western bats, including the little brown bat, have been observed roosting in smaller, more dispersed groups. Researchers still don’t know where California bats spend the winter or how many bats are typically in these roosts. Where exactly they live is one question that Osborn’s team hopes to answer.

Potential Treatments

Treatments do exist for combatting the fungus and the disease it causes. For example, one study published in the journal Nature found that the fungus is easily killed by ultraviolet light. Another study from the same journal found that a probiotic treatment could slow the decline in bat colonies where the disease is present.

And there’s emerging research into a potential oral vaccine, which could be administered by a topical cream or spray. Bronwyn Hogan, a wildlife biologist with the U.S. Fish and Wildlife Service, says the treatment is promising because bats are constantly grooming and cleaning their fur.

Hogan says wildlife managers may respond with a variety of these treatments, depending on the place and circumstances, but they need to be careful not to cause collateral damage, especially inside caves, which have delicate ecosystems. 

“There is no ‘silver bullet,’” she said.  

Wildlife officials are enlisting the help of the public, asking them to report any sightings of dead bats or bats that are active in cold places during the winter. 

Pat Seiser, the chief physical scientist for Lava Beds National Monument, said news of the fungus is spreading among cavers, too.

“We're actively getting the message out to decontaminate gear and use dedicated equipment within the caving community,” said Seiser.

Of the 25 different species of bats in California, there are six that have carried white-nose syndrome in other states, including the little brown bat. The others are the big brown bat, cave bat, long-legged bat, western long-eared bat and yuma bat.

Another four species present in California tested positive for the fungus but have not, so far, shown signs of the disease. These are the Mexican free-tailed bat, Townsend’s big-eared bat, the silver-haired bat, and Western small-footed bat.

Biologists were able to detect the fungus in very low levels by using a polymerase chain reaction, a common molecular biology technique that uses enzymes to unzip DNA and replicate it with RNA. With this technique, scientists can rapidly synthesize and amplify even tiny bits of genetic material.  

They are holding onto the hope, however slim, that the disease won't take hold here.

“I'd be really happy if the disease actually doesn't show up,” Osborn said. “The next couple of years are going to be very interesting to see what actually happens here.”

Bats are important for ecosystems because they consume mosquitoes, bugs and pests that damage food growing on farms. Bats save farmers and land managers $3.7 billion in pest management costs annually, according to an estimate of their economic impact from 2011.