We all know Dracula, no matter how he’s characterized in paranormal romance or screen horror, has never been sick a day in his life. In fact, any vampire is darn hard to kill, requiring a stake to the heart and/or exposure to the sun and/or beheading. A mere bout with the Romanian flu just isn’t going to get the job done.
|Good looking--and healthy, too!|
Turns out the reason so many fictional vampires are immortal and immune to human diseases may be based in a real biological quirk of their flying, furry familiars—bats. A study by researchers at the University of California, Berkeley, published this month in the journal eLife, shows that bats’ immune systems have a unique ability to quickly wall off cells from invading viruses using interferon, thus protecting the host bats from infection.
The viruses respond by reproducing at a higher rate, which hardly affects the bats at all but is bad news for any other mammals the bats may encounter. The viruses multiply and become much more deadly for mammals that do not have the bats’ super immune systems. Thus bats serve as a reservoir and, worse, an incubator for pathogenic viruses in the wild that infect intermediary mammal hosts and eventually work their way toward human populations.
The diseases that follow this pathway are a rogues’ gallery of highly transmissible assassins: Marburg, Ebola, SARS, MERS and quite possibly the newly emerged coronavirus, 2019 nCoV. "The bottom line is that bats are potentially special when it comes to hosting viruses," said Mike Boots, a disease ecologist and UC Berkeley professor of integrative biology. "It is not random that a lot of these viruses are coming from bats. Bats are not even that closely related to us, so we would not expect them to host many human viruses. But this work demonstrates how bat immune systems could drive the virulence that overcomes this."
In the case of Ebola and Marburg in Africa, monkeys and chimpanzees are most often the intermediary mammal hosts between bats and humans. In the case of SARS in China, a species of civet (a wild cat-like mammal) was the intermediary. In MERS, camels were the intermediate host. The intermediary host or hosts have not been conclusively identified in the case of the new coronavirus in China, but the source has been narrowed to a wildlife market in the city of Wuhan, where the disease first originated and is still centered.
Environmental damage and habitat destruction, the result of the incursion of human populations, increase stress on bat colonies. Instead of making individual bats more vulnerable to viruses, stress makes them shed higher numbers of viruses in their saliva, urine and feces than normal, infecting even more intermediaries and becoming a threat to those very humans.
The research confirms this. "Heightened environmental threats to bats may add to the threat of zoonosis*," said Cara Brook, a postdoctoral Miller Fellow at UC Berkeley and the first author of the study. Brook also works with a bat monitoring program funded by DARPA (the U.S. Defense Advanced Research Projects Agency) in Madagascar, Bangladesh, Ghana and Australia exploring the link between loss of bat habitat and the spillover of bat viruses into other animals and humans, according to an article about the study in Science Daily.
|A miracle of anti-inflammatory, virus-fighting evolution.|
The researchers also noted that bats have a longer lifespan than other mammals their size, despite the higher metabolism and activity level required for flight. Some bats can live as long as 40 years, according to the study, while the typical rat only lives about two years. The secret to the bats’ longevity may lie in their ability to eliminate damaging inflammatory “free radicals” produced by their high metabolism. The same mechanism that allows this anti-inflammatory response kicks in with protective interferon when the bat’s body is invaded by a virus. Long life and disease protection in one mechanism!
I suppose it’s possible that in the dim past our more observant, but less scientific ancestors noticed that their sheep or cattle bitten by bats sometimes died of some strange disease while the bats themselves seemed to thrive unharmed. Combine that with the tales of a bloodthirsty Romanian nobleman with a reputation for impaling his opponents on the battlefield and a countess with a taste for the blood of virgins and you have the beginnings of the vampire legend. Add a bat’s everyday supernatural long life and ability to overcome disease and, well, all you need is a tall, dark guy with irresistible good looks and an exotic accent to kickstart your new paranormal romance series!
Information for this post adapted from “Coronavirus Outbreak Raises Question: Why are Bat Viruses So Deadly?” Science Daily, February 10, 2020. https://www.sciencedaily.com/releases/2020/02/200210144854.htm