you can get an american product called prevent-a-mite, an aussie product called top of descent ( from herpshop), you can also dilute down a product called orange medic available from your chemist (used for head lice i think) but look for the one without tea tree oil as it can be dangerous for the reptile. there is different instructions for using each of the above, some you use on the cages, and some are suitable for use on the animals themselves.
i have heard of people using a diluted bleach solution to clear the cage, but obviously dont use it on the animal.
mites can come in if you use untreated branches, mulch, rocks or anything from outside in your cages, but it could also be transmitted simply by you having picked something up outside and then handled your snakes. if you are putting branches etc into your cage you can always sterilise them by either nuking them in the microwave, in the oven or cleaning them with one of the above mentioned products, or even complete submersion in a drum of water for a few days to kill anything off that is living internally!
you should also implement some level of quarantine, or even a cleaning order with your animals, start using hand sanitiser between cages, cleaning handling gear between cleans etc as a way of minimising the risk of any future tramsmission.
hope this helps you out mate!
...i also have a couple of questions...how can i prevent it from happening again and how do they get mites??? thanks dave 
