I do recall some folks having problems with Eco Earth, however--it traps a lot of moisture, and folks were having snakes with skin infections due to being on it. So, I'd advise caution with it, based on that.

No beddings transmit snake mites. They ONLY come from other snakes and reptiles. They do, however, wander absolutely everywhere, so if there's an infected animal on the premises, anything you bring home from there might have hitchhikers. On the outside, though--not inside the sealed bag.

You may have heard wood mites mentioned occasionally. Mites are a HUGE group of animals, and there are zillions of specialized mites out there, which can be found in almost anything. (Your own bed is loaded with microscopic dust mites, and your skin is home to some interesting varieties as well). Wood mites don't harm reptiles in any way. The only mites that are of concern are those that chew on the animals or feed on their blood, and those are usually fairly specialized.

You may find wood mites in some beddings, but unless something very peculiar has happened, you won't find snake mites in there.