How Bats Survive Deadly Viruses

Bats are often the source of deadly viruses. So why is it that they hardly show symptoms or get sick? As Covid-19 (which likely originated in bats) sweeps the world, scientists are studying the impeccable immune systems of bats in hopes of finding explanations for their unique ability to combat diseases and advancing disease spread prevention efforts.

Bats have been outsmarting viruses for 65 million years [1]. They have also been found as the likely source of many disease outbreaks, from the SARS-CoV-2 (COVID-19 outbreak) virus that has infected upwards of 15 million people to the MERS virus that has infected upwards of 800,000 people [2].

Bats are so diverse that they make up ~¼ of all mammalian species! With 1400+ species, bats are the second most diverse group in the world, and they live on every continent besides Antarctica [3]. Their abundance, ability to fly, and close proximity to farms and neighborhoods allow them to easily spread viruses [4].

In this blog post, I’ll delve into three studies regarding bats and their abilities to survive deadly viruses.

Bat1k Project:

The Bat1k project was launched in 2017 with the goal of sequencing the genomes of bats. Thus far, scientists have sequenced the genomes of six species of bats [5]. DNA sequencing is vital in determining which sections of DNA contain genes and which sections contain regulatory instructions [6]. This information will help us understand how bats have evolved to so effectively fight off viruses!

The findings are an “excellent starting point for understanding the superstar immune systems of bats,” says Laurel Yohe, a postdoc at Yale University who studies bat evolution [1].

The Bat1k findings have found that bats have disabled at least 10 genes that are used to initiate inflammatory responses against infection [5]. As inflammation itself can be harmful to the body, this response to infection likely helps bats fight off infections in the long run [4].

Additionally, bats were found to have extra copies and modifications of antiviral genes, indicating that they have a high tolerance for disease. Scientists also noticed that their genome included DNA from past viruses the bats had contracted, suggesting that the virus integrates itself into the bat’s genome!

“The [Bat1k] findings highlight bats’ ability to tolerate and survive viral infections more efficiently than other mammals,” says Sharlene Santana, an evolutionary biologist at the University of Washington, Seattle.

DNA Sensing in Bats (China & Singapore):

This study analyzed how bats handle DNA sensing, which dictates anti-viral responses in organisms. In Xie et al., 2018, scientists discovered that bats may be able to survive viruses because their evolutionary adaptations to flight have strengthened their immune systems [7]!

Flight requires a copious amount of energy, and consequently, cells in the body break down and release bits of DNA into parts of the body where they’re not typically found. All mammals have ways to identify and respond to foreign bits of DNA, as viruses are. However, in bats, this system has weakened, causing little to no inflammation as the bat fights the virus. This discovery parallels that of the Bat1k project.

The researchers write, this weakened response may allow them to maintain a “balanced state of ‘effective response’ but not ‘over response’ against viruses [7].”

Modeling Bat Immune Systems (UC Berkeley):

In a 2/2020 study, scientists at UC Berkeley modeled the immune systems of bats [8]. They found that when a virus infects a bat, bat cells immediately release interferon (communicates with the body’s defense system in terms of the replication of viruses within host cells), and other cells “wall themselves off [9].”

In bats, this process actually allows the virus to reproduce faster, but bat immune systems are able to essentially live with the virus until fighting it off, but the increased virulence that has now developed in the bats becomes a nightmare when the virus reaches other animals with tamer immune systems [10].

“Some bats are able to mount this robust antiviral response, but also balance it with an anti-inflammation response,” said Cara Brook, a postdoctoral Miller Fellow at UC Berkeley and the first author of the study. “Our immune system would generate widespread inflammation if attempting this same antiviral strategy. But bats appear uniquely suited to avoiding the threat of immunopathology [11].”

Conclusion? Bats have truly one-of-a-kind immune systems that have likely evolved from their bodys’ ability to cope with the strenuous activity of flight. Viruses are able to reproduce at fast rates in bats because of their inactive inflammatory response to foreign DNA. And because of this same inactive inflammatory response, bats are able to slowly but surely fend off the virus with showing little to no symptoms.

These studies regarding the immune systems of bats will help us better understand both disease prevention efforts and the “superhuman” immune systems that may have implications towards vaccine development for humans!

Here’s a great comprehensive video on the topic:

Thank you for reading this piece on how bats are able to survive deadly viruses. I hope you enjoyed it! I encourage you to leave a comment and/or start a discussion in the section below!

Feel free to contact me at brainsproutblog@gmail.com and follow the blog @brainsproutblog on Twitter and Instagram for updates!

Bat1k Project:

DNA Sensing in Bats (China & Singapore):

Modeling Bat Immune Systems (UC Berkeley):

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