They are annoyingly common actually, especially on bps for some reason. If you keep a lot of snakes, it's not a matter of if, but when you get a snake with them, I have 12 snakes all together and 2 had mites, both bps. The good news is that mites aren't the apocalypse bringer most people make them out to be as long as you catch them before their numbers get really high. Good quarantine and a good eye prevent them from becoming too much of an issue.