Bat ‘discotheques’ could be key to solving the next pandemic

Bats carry some of the deadliest zoonotic diseases that can infect both humans and animals, such as Ebola and COVID-19. In an article recently published in the journal Cellular genomicsA Texas A&M research team has revealed that some species of bats are protected from the viruses they carry because they typically exchange immune genes during seasonal mating swarms.

“Understanding how bats developed viral tolerance can help us discover how humans can better combat emerging diseases,” said Dr. Nicole Foley, of the Texas A&M School of Veterinary Medicine & Biomedical Sciences (VMBS). . “As genomicists, our work often lays the foundation for research by scientists who directly study the transmission of viruses. They may develop vaccines for diseases or monitor vulnerable animal populations. We all depend on each other to keep a step ahead of the next pandemic.”

Because bats are often immune to the diseases they carry, Foley and Dr. Bill Murphy, professor in the Department of Veterinary Integrative Biosciences at VMBS, believe that studying bat immunity could be the key to preventing the next global pandemic.

“Due to the COVID-19 pandemic, forecasting and preventing outbreaks is a priority for researchers and the public,” Foley said. “Several species of bats tolerate viruses that are harmful to human health, which means that they become reservoirs of disease: they carry the viruses, but above all, they do not develop symptoms.”

The secret to swarming behavior

To find out exactly how bats developed their tolerance to these deadly viruses, Foley, Murphy and their international research partners mapped the evolutionary tree of Myotis bats, which they knew would be crucial in trying to identify the genes likely to be involved.

“Myotis bats are the second largest genus of mammals, with more than 140 species,” she said. “They are found almost everywhere in the world and harbor a wide diversity of viruses.”

To add to the difficulties of determining species relationships, Myotis and other bat species also engage in swarming behavior during mating.

“You can think of swarming behavior as social gathering; there’s a lot of flight activity, increased communication, and interspecies mixing; for bats, it’s not unlike going in a club,” Foley said.

What complicates matters for researchers is that swarming creates an increased number of hybrids, individual bats with parents of different species.

“The problem with Myotis bats is that there are many species, about 130, but they all look the same,” Foley said. “It can be very difficult to tell them apart from each other, and hybridization makes it even more difficult. If we try to understand how these bats evolved in order to understand their immunity to disease, being able to tell who is who is very important.”

Unraveling hybridization

With this in mind, to create a map of the true relationships between Myotis bats, Foley and Murphy first unraveled the genetic code of hybridization so they could more clearly distinguish which species were which.

“We collaborated with researchers from Ireland, France and Switzerland to sequence the genomes of 60 species of Myotis bats,” she explained. “This allowed us to determine which parts of the DNA represented the true evolutionary history of the species and which parts arose from hybridization.”

With this part of the puzzle solved, the researchers were finally able to examine the genetic code more closely to see how it might shed light on immunity to the disease.

They found that immune genes were among those most frequently exchanged between species during swarming.

“Swarming behavior has always been a mystery to researchers,” Foley said. “We now better understand why this particular behavior evolved, perhaps to promote hybridization, which helps spread beneficial immune gene variants more widely in the population.”

New questions for researchers

Foley and Murphy’s findings opened the door to new questions about the importance of hybridization in evolution.

“Hybridization played a much larger role in our findings than expected,” Foley noted. “These results led us to question the extent to which hybridization has so far obscured genomicists’ knowledge of the evolutionary history of mammals. We now hope to identify other cases where hybridization has occurred in mammals and see what we can learn about how they are related and even how and why genomes are organized the way they are,” she said.