Mites can come from anything. It can come from feeders, bedding, new reptiles, etc. I'm not sure on the scientific name. Eggs can lie dormant until proper conditions arise(I.e. survive freezing process). And the nymph stage is airborne. So they really can get around fast.
They can spread and reproduce very quickly. You can have one mite one day and an infestation by the end of the week.
I recommend changing all substrate to paper towels and have your set ups as simple as possible. (take out all accessories except the water bowl and sanitize everything with bleach and hot water). The paper towel makes it easier to see the mites. Also, its always good to treat all newcommers, no matter where they come from. It's a good preventative measure. I PAM each new tub I set up for a new arrival.
Good thing about reptile mites is that its species specific. So you don't have to worry about them infesting you.
Pam is the best and most efficient route. In the mean time, you can soak your snake in a warm bath with a drop or two of dish soap. This will ease her discomfort as well as kill some nasty mites.
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