my snauzer is white and they have a lil dryer skin right.he has fleas horridly. but hes a bit betta. but we noticed he has white flaces of nasy crust on his legs. he had a bath today, but its the same.

what r scabies?
how do they get it?
how can you tell if your dog has them?
how to treat it?
what can happen to him???

any help is much needed! thanks!!!!!!!!!!!!!!!!!!!!!!!!!!!