Welcome back to Ferrebeekeeper’s Halloween special feature concerning bats! If you like you can check out last week’s posts concerning bat mascots, Honduran white bats, and the Chinese good luck symbol Wu Fu. Bats are exceedingly wonderful and I love them…but where is the chilling Halloween horror?

Well, bats do have a dark side (at least to humans, when we eat them or intrude too far into their world). They are an infamous vector for zoonotic viruses which jump easily to closely related mammalian species. Although we are most attuned to this year’s worldwide pandemic, covid 19 (which seems not to have come from snakes, but from horseshoe bats) both the SARS and MERS epidemics were caused by bat-borne coronaviruses. Less memorably, bat coronavirues also jumped into the farmyard and caused a serious viral epidemic in China’s pigs. Bats are the natural reservoir for Ebola, Hendra virus, Nipah virus. A single bat can host many different viruses without getting sick. Because they live in close proximity in (sometimes enormous) colonies, viruses readily infect huge numbers of bats. Additionally bats are unlike other small mammals such as rodents and shrews in that they have long lifespans. Most bats can live 20 to 40 years (although, sadly, most do not because, as any World War I aviator could tell you (if any were alive), flying presents certain dangers).

All of this begs the question of why bats are so prone to viruses and yet also so resistant to their effects. Zoologists and Cell biologists are only beginning to unravel this puzzle, but what they have found presents a fascinating picture of the interplay between cellular biology and the physical characteristics of animals.

In the course of metabolizing, reproducing, fighting diseases and so forth, cells are sometimes destroyed in novel ways which release free DNA into places it should not be. This is potentially a big problem and animals cope with it through a mechanism known, sensibly, as DNA-sensing. Alas, this is about as far as I can reasonably describe this process, but you can check out a diagram which explains cytosolic DNA sensing machinery in humans below.

Perhaps this diagram also explains why molecular biologists sometimes find it difficult to characterize what they do in pithy buzzwords

Uhhh…at any rate, among mammals bats have uniquely rigorous physiological demands due to the energy requirements of flight. The high-impact demands of flying lead to substantial cellular damage, but also preclude the solution other mammals adapt (which, as you can see above, is inflammation). If bats were prone to inflammation to the same degree as other placental mammals, they would lose their ability to fly. Instead they have lost various genes and have a more muted response to miscellaneous DNA. This diminished ability to clean up random intracellular DNA makes our fluttery friends more prone to all sorts viruses, yet they have found some other way to endure viruses without over-responding.

As you can probably tell, the cytological processes we are talking about seem to play huge and important roles in cancer, autoimmune disorders, and a host of chronic metabolic disorders like heart disease & diabetes. Not only would it be immensely beneficial to understand bats’ seemingly unique DNA sensing apparatus (and response) in terms of virology and epidemiology, it might bear fruit in many other branches of medical inquiry.

Horseshoe Bat

Alas, this sort of blue skies research (or should we call it dark skies research in honor of our nocturnal subjects?) is exactly the sort of thing which enormous companies are disinterested in and which the Federal government has turned its back upon. Fortunately (?), the Chinese government is extremely interested in finding out more about but-human zoonoses and has been diligently working to figure out more about DNA sensing and concomitant immune response in chiroptera. In fact, if the grotesque bowdlerization of the subject which I have presented in this post does not satisfy your curiosity, you can read a rather fine (albeit technical) Chinese article from 2018 about the subject.