How Bats Can Carry Diseases Without Dying From Them

Ebola. Middle Eastern Respiratory Syndrome (MERS). Marburg virus. Severe acute respiratory syndrome (SARS). Nipah virus. The list of infectious diseases carried by bats is over one hundred. Yet it’s been a mystery why none of them seem to do any harm to the carriers themselves. A new study found a surprising explanation that may one day give humans some of the same immunities.

According to a report published this week in the Proceedings of the National Academy of Sciences (PNAS), researchers at the CISRO (Commonwealth Scientific and Industrial Research Organization) Australian Animal Health Laboratory studied the immune systems of Australian black flying foxes in comparison to those of humans.

Whenever our body encounters a foreign organism, like bacteria or a virus, a complicated set of immune responses are set in motion, one of which is the defense mechanism known as innate immunity.

Dr. Michelle Baker, bat immunologist on the project, also points out that both bats and humans (and mammals in general) fight infections with interferons – proteins released by cells in response to an invasion by viruses, bacteria, parasites and other pathogens. Humans have a dozen interferons that are released upon infection. Bats, with their superior immunity, have only three. What’s their secret?

Both bats and humans have Type I interferons that are the heavy-duty killer cells. It turns out that bats leave their immune systems active at all times while humans only turn them on when we need them. So the solution for humans is to load up on Type I interferons 24/7, right? Not so fast, says Dr. Baker.

In other mammalian species, having the immune response constantly switched on is dangerous - for example it's toxic to tissue and cells - whereas the bat immune system operates in harmony.

All of that internal cell-killing, while necessary, makes humans feel sick, while bats are unaffected because their cells manage to somehow live in constant peace and harmony. That's the next step towards bat-like immunity the researchers will attempt to solve. Humans may not be able to do that with each other but someday we may at least be able to get our cells to live in peace and harmony.

All it takes is to act a little batty.