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Dr. Vikram Misra, U of S veterinary microbiologist at the Western College of Veterinary Medicine. Photo by David Stobbe / Stobbe Photography.

Stressed bats can increase spread of deadly viruses

Bats are responding to stress from such things as habitat destruction, lack of nutrition and infections by increasing the production and shedding of viruses that cause serious and often fatal diseases in humans and other animals.

That’s the finding in a paper published Oct. 19 in Nature—Scientific Reports authored by University of Saskatchewan veterinary microbiologist Vikram Misra led an international team that included PhD student Sonu Subudhi and research assistant Noreen Rapin of the USask Western College of Veterinary Medicine’s bat zoonosis laboratory.

“Bats have a really benign relationship with their viruses until you stress them through secondary infections or other stressors,” said Misra. “That’s when they start producing and shedding more viruses.”

The little brown bats collected from caves in Manitoba for the study are common to the Canadian Prairies.

The researchers found that white nose syndrome (WNS), a deadly fungal disease that has killed millions of bats after it was recently introduced to North America, causes bats to increase their production of coronaviruses that are harmless to bats but potentially deadly for humans and animals.

WNS, found mostly on the wings and skin of bats, suppresses the immune response that keeps the viruses in check, and increases virus replication in the guts of bats by as much as 60 times. This immune response occurs even when the bats are hibernating.

While the causes for spillovers to other animals are not known and likely very complex, an increase in virus shedding by bats increases the chances of spillovers.

This is the first study to examine the systemic effects of co-infection on either bat coronavirus or white nose syndrome.

In recent years, several viruses that cause no apparent illness in their bat hosts have spilled over from bats to people and other animals causing often-fatal diseases such as Ebola, Severe Acute Respiratory Syndrome (SARS), Middle East Respiratory Syndrome (MERS), Hendra, and Nipah. These viruses are thought to have originated in bats.

“Understanding the host-pathogen interactions between bats and coronaviruses would help us predict or manage the risk of spillover,” said Misra.

The team involved 14 researchers from Usask, Trent University, and the University of Winnipeg. Funding for the study was provided by grants from the United States Fish and Wildlife Service, Natural Sciences and Engineering Research Council of Canada, USask’s One Health Initiative, and a post-doctoral fellowship from the German Academic Exchange Service.

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