Snakes in captivity have been known to get mites from prey items.... (read on.. )

You drop the mite carrying rat in the cage, and it drinks the water and/or poops in the water. The snake drinks the water, and the mite eggs come out when the snake deficates. The snake crawls over its own poop, and whammo....

That's just one way...

You can prevet mites with a product called Provent-A-Mite. (We all call it PAM)

It can be purchased directly from the factory that makes it at http://www.pro-products.com

Its good for infestations or just preventative use. It'll take care of the eggs, and prevent mites from becoming a problem.

Hope this helps...