how can bats be hosts to a range of deadly viruses without getting sick?
In: Biology
It’s mind blowing but the answer boils down to the fact that bats are not really well adapted for flight.
When you learn birds, you learn a lot of stuff they have to adapt for flight: special white muscle (that’s why chicken breast is different from steak), big breast muscles etc. Bats don’t have those.
In fact bats are so poorly adapted to flight so they have continuos muscle pain, same what you get after a thorough training. But continuously. And that is in fact a muscle inflammation. So to keep things in bay, bats evolved another kind of response to this inflammation: they evolved to tune down their immune system to turn off the inflammation.
Another mind blowing fact is that many virus nowadays are kinda harmless and the disease and the harmful symptoms are often coming from the immune system. Why is so then? Well, there are still bad viruses and the immune system cannot decide which one would be a peaceful virus and which one would be harmful. So there’s a first shoot then ask policy, and over our evolutionary history this might have been the good strategy. But as a sad side effect, many times it’s not the virus that’s deadly but our immune reaction. Unfortunately we do not un-evolve or tune down our immune system just to test whether nowadays viruses are safe. But you see, bats did because they needed.
And so immune system is a package deal, you cannot tune it down just for muscle inflammation. That’s why bats have less symptoms from viruses and so they peacefully co-exist. (Until they find a deadly virus where the virus itself is deadly because then they have no defense and die.) Okay they don’t have entirely no-defense but way more lazy than ours. And so that allows for viruses that are deadly in us (often because of our reaction), to thrive in bats.
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