Bats, unfairly maligned and demonized, have lived on this planet for more than 50 million years. Their long evolutionary history has had the unfortunate side effect of making them reservoirs for numerous pathogens. This includes all of the world’s most dangerous viruses. Included in these are the Ebola virus, Hendra virus, Nipah virus, and the current SARS-CoV-2 virus that causes COVID disease.
Ecological importance Bats are the second-largest group of mammalian biodiversity, making up about 20% of all mammal species. Yet their amazing diversity is key to ecosystems worldwide and is the foundation of life on earth.
New research sheds light on this complicated dynamic between bats and the pathogens that infect them. Despite their reputation as disease carriers, bats are still gentle creatures that groom themselves like house cats. This self-cleaning habit likely plays a role in their resistance to infection. Their unique physiology and behavior make them prime targets for various diseases, including white-nose syndrome, a fungal infection that particularly affects hibernating bat populations.
Bats and Their Viral Load
Bats are unique among mammals in the enormous diversity of viruses they harbor, a consequence of their unique long evolutionary history and also of flight. And as we’ve seen with viral diversity such as coronaviruses, flight is an incredibly important factor. Most notably, it allows them to traverse wide spaces and engage with disparate microhabitats and possible hosts. Pathogen diversity Animals, particularly bats, host an incredible diversity of pathogens. Scientists have described more than 1,400 species globally.
Pathogen spillover from bats has recently received a lot of attention. This focus is particularly acute in the wake of recent global health emergencies. Pathogens that jump from other species to bats are likely to be most pathogenic when they first transition to a new host species. This phenomenon highlights the critical need for understanding bat biology and ecology in the context of emerging infectious diseases.
“Infectious disease has been the biggest factor in all of evolution.” – Jim Wellehan
Wellehan’s words underscore just how dramatically infectious diseases can impact bat populations. These diseases can influence bats’ interactions with other species, including humans. As bats continue to adapt to their environments, they have developed unique immune responses that allow them to coexist with these pathogens without succumbing to disease.
The Magic of Bats
Bats enchant us with their incredible echolocation prowess. Their whimsical, mystical, enchanting reputation owes itself to these characteristics as much as the folklore that has developed around them. As Wellehan told news site hereandnow.org, people want to know the reasoning behind the enchantment of bats. He states, “People are always looking for an excuse (as to) why bats are magic, and the truth is bats have just been exposed to a lot of stuff and selected for those genes accordingly.”
This rapid genetic selection process has prepared bats with unique and powerful immune systems that can halt a wide variety of pathogens in their tracks. Bats have certainly been under some evolutionary pressure to adapt for millions of years. This evolutionary arms race has led to an incredible dynamic in their unique biology and the viral inhabitants they possess.
“When I first learned about Darwin and evolution, ‘survival of the fittest,’ I assumed, meant ‘smartest and fastest and strongest,’ but if you look at our genomes, turns out that’s wrong.” – Jim Wellehan
Wellehan’s observations raise difficult questions about commonly accepted ideas of evolution and survival. Bats are evolution’s masters at finding solutions to harsh conditions. Such adaptations highlight the powerful influence of genetics on species’ responses to environmental stresses, particularly from pathogens like infectious diseases.
Conservation Challenges
Though bats are an essential component of our ecosystems, they are still plagued by multiple threats that threaten their existence. Conservation initiatives help protect the remaining bat species at stake. Additionally, they protect human health by mitigating the risks associated with pathogen transmission to humans. As white-nose syndrome continues to wipe out bat colonies throughout North America, the bats’ need for conservation efforts has never been more urgent.
Collectively, these efforts will help stop the decline of these important mammal populations and keep them helping our ecosystems prosper. Successful conservation strategies include habitat protection, public education, and research into bat biology and ecology. It’s important to get a better understanding of how bats respond to these pathogens. Understanding these factors can help us prevent spillover events that cause zoonotic diseases.