Other treatment options are Horse Dewormer paste(Ivermectin) from feed stores. Feed a rice grain size dose to each rat once week for 3 weeks.
I seriously tried this once and all mites were gone after a day. But I still treated the full course.
You can also get Diatomaceous Earth (food grade) from health stores/garden centers/feed stores and sprinkle your bedding and powder your animals (just keep away from eyes and nose). Diatomaceous earth is all natural and non-toxic. Its harmless to mammals and birds. But it shreds anything with an exoskelleton and dehydrates them to death.