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!
Cheers, Donna
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
You can add one more to that pile of infections - Hendra. It's very often fatal and the intermediary host is horses. They become infected when they eat grass contaminated by flying fox droppings. It had a devastating affect on any sport involving horses for at least a year in Australia. Killed a few vets who treated horses, properties were quarantined and people couldn't move horses across state borders etc.
ReplyDeleteA vaccine was developed but it's still a potential killer.
Wow, Greta. I hadn't heard about Hendra, but probably because we don't have flying foxes here. Pretty frightening, especially for vets!
DeleteWe did have a severe outbreak of equine herpes in the last few years that also resulted in quarantines and restricted movement of horses, especially across state lines and between racetracks, but I don't think that particular malady could be passed to humans.
"Fascinating," as Spock would say. Around these here parts, bats are feared for carrying rabies, but I never realized they were potential viral warehouses.
ReplyDeleteI wonder if, due to the tendency of their species to congregate together in "swarms," if nature provided this super immune system through natural selection, because only the survivors of early "batdemics" would have passed down their resistance genetics to new generations. It seems likely.
Hmmm, definitely some SFR plot bunny fodder here!