North American bats may be susceptible to SARS-CoV-2

This is bad news for bats and humans.

 

After the initial outbreak of COVID-19 in Wuhan, China, late last year, scientists rushed to uncover the disease’s origins. Studies showed that SARS-CoV-2, the virus that causes COVID-19, likely arose in the Chinese horseshoe bat, jumped to another animal, and then spread to humans. Now, researchers are concerned that humans, ironically, might spread SARS-CoV-2 to a new host: bats in North America. This is bad news for bats if the virus turns out to be deadly. And if bats can transmit the virus back to people, it’s bad news for humans, too.

As the virus continues to spread nationwide, scientists are ramping up their efforts to protect local bats. “Immediately, researchers started asking, ‘Do our bats have this? If not, could we give it to them?’ ” said Lauri Hanauska-Brown, chief of Montana’s Fish, Wildlife and Parks Nongame Wildlife Management Bureau.

A study estimated that 50% of little brown bats handled by researchers actively shedding the virus could be exposed to the disease, and 17% may become infected.
Peter Thomson/La Crosse Tribune via AP

This spring, experts in fields including virology and wildlife disease assessed whether SARS-CoV-2 can harm North American bats, which include over 40 different species. The results, released in June, indicate that the virus could spread from humans to bats. However, there are still many questions that scientists must answer in order to protect these animals from a potentially fatal virus.

Bats have a reputation for being virus reservoirs, partly because they have specialized immune systems that allow them to carry viruses without becoming sick. Most of these viruses, including many types of coronaviruses, have evolved alongside the animals for millions of years. But a new virus can still harm bats; consequently, scientists worry that North American bats may be susceptible to SARS-CoV-2, which humans could transmit through handling bats or going into caves.

To better understand the risk that SARS-CoV-2 poses, a panel of scientists from the U.S. Geological Survey, U.S. Fish and Wildlife Service and the nonprofit EcoHealth Alliance recently produced an assessment report. The scientists drew on their expertise to answer questions, such as how many bats could be infected by human researchers, wildlife rehabilitators and pest managers between now and hibernation season, and how fast infected bats might spread the virus to their offspring. They estimated that 50% of bats handled by researchers actively shedding the virus could be exposed to the disease, and 17% may become infected. Additionally, there is a 33% chance of the virus spreading within the bat population once it’s been introduced.

The researchers found that if people wear protective equipment, like masks and gloves, their chance of circulating the virus drops by about 95%.

Luckily, there are ways to help stop the spread. The researchers found that if people wear protective equipment, like masks and gloves, their chance of circulating the virus drops by about 95%. However, this assessment has many limitations, including the fact that just one species — the little brown bat — was considered, and only during the active season, when bats aren’t hibernating. Researchers like Hanauska-Brown frequently interact with bats during the winter, when the animals hibernate; it’s unclear whether chances of transmission are higher during that time.

Researchers are also limited by the general lack of information on how SARS-CoV-2 transmits between people and animals. “We do know that some animals — for example, cats — can be infected (with SARS-CoV-2) naturally, presumably from humans,” said Erica Schumacher, an outreach veterinarian from the University of Wisconsin-Madison. But studies on the virus in bats are scarce, with one from Germany suggesting that fruit bats may be susceptible to SARS-CoV-2 infection in a laboratory setting. Without knowing how North American bats react to the virus, it’s hard to determine the extent to which it’s a major threat.

This isn’t the first time a disease has threatened bat populations in the U.S. Since 2006, white-nose syndrome has killed around 7 million bats from eastern Canada to Texas; in some areas, it’s wiped out entire colonies. The fungus that causes white-nose syndrome was discovered for the first time in eastern Montana this June. Scientists like Hanauska-Brown are keeping an eye on its spread with the help of local cavers, including Ian Chechet, the president of a caving club called the Northern Rocky Mountain Grotto. “We go into caves and pretend we’re detectives: ‘How did this get here? How did this happen?’ ” he said. “We’re pro-furthering science.” Hanauska-Brown plans to contact the cavers if biologists need to conduct fieldwork on SARS-CoV-2. And if the cavers see anything unusual during their excursions, like sick bats, they’ll notify the researchers.

In the meantime, researchers in Montana and many other states have suspended fieldwork that involves capturing or handling bats. With such limited research, scientists are basing many of their risk-management responses on a lot of uncertainties, said Hanauska-Brown. “Until we get more information, we need to be extremely cautious and not put ourselves or the bats at risk.”

Helen Santoro is a freelance science journalist based in Gunnison, Colorado, and is a former HCN editorial fellow. Follow her @helenwsantoroEmail High Country News at [email protected] or submit a letter to the editor.

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