I actually never brought it to my home. I took it elsewhere, leaving it in the same container that they put it in. It is a Christmas gift and I have no place to hide it here until then. I also never held it, so no chance of cross contamination there either. I just noticed the black spots on it upon looking at it closer in it's container. THANK GOODNESS!!!! 
The new one I did, however, hold this time and take a closer look at before leaving the store. This place even made me sanitize my hands before handling the snake. She's gorgeous and looks extremely healthy and lively.
I understand about the off the wall information that pet stores give. They not only tell you that thing about it only getting as big as the cage with snakes, but with everything else too. I have one pet store here that tried to tell me the turtles will only get as big as the tank I put it in. That pet store also doesn't like me much because, I tell them how wrong they are with every bit of information they try to give me......LOL. The baby bunnies they sell will not get any bigger than they are right now. YEAH RIGHT!!! They are only about 5-6 weeks old when they get them. Who they trying to kid. Hence the reason I don't buy anything from them either. I just like to go in there and harass 'em..........LMAO.
Thanks for the heads up, though. Not a lot of people think about that when they bring another animal into their homes where others exist. I learned my lesson about that years ago when I brought another cat in. She got sick and got a close call with it possibly being something that could have wiped out my entire group of cats. Thankfully they finally found out what it was and my other cats could not get it. But it was a harsh reality check on my part.
>>Well now that the mites have been introduced... your new snake will get them, your old snakes will get them, and any reptile in the room and possibly in the house will get them until you completely take care of the problem. I know this didn't answer your original question of how to get rid of them but that is because I am unsure. I know there are several sprays but someone else can better answer this for you.
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>>0.1 Snow Corn "Hope"
>>1.0 Ball Python "Wilson" (Castaway)
>>1. Orange Albino Black Ratsnake "Chunk" (Goonies)
>>.1 Orange Albino Black Ratsnake "Peaches"
>>0.0.1 Mexican Black Kingsnake "Onyx"
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Whatever makes you smile
Whatever makes your daily battle seem worthwhile
Whatever makes you feel like your time is well spent
Whatever causes you to be content
Whatever makes you feel alright
Whatever gets you through the night
Do whatever you want to do
Just be sure you follow through