How do snakes get mites?

I read people posting about mites a lot. How exactly do BPs (any snake for that matter) get mites? Also, what causes respiratory infections?

I think mites are can be caused by dirty cages, sometimes they can pick them up on certain carpets or out in the grass. Respiratory infections are caused by a number of things, such as too much heat, not enough heat... too low or too much humidity, dirty cages... just anything really.

Wild snakes get em from the wild, and then they get passed about like an epidemic. Pet stores don't help by using the cage many times with no washing.

For future reference, what are the symptoms of mites?

Only reason I ask is I have a wild / burned (from the san diego wildfires) kingsnake at my house currently being nursed back to health.

I just want to know what to look for so I don't run the risk of my BP getting anything. Oh and both snakes are obviously in seperate cages and in seperate rooms in the house. Thanks for your help. =)

Excessively soaking in it's water is one, just look at it's body for them.

I found a brief description in the husbandry section. I just need to look for small flea things according to it. Thanks for the water tip though.