On top of the provent a mite (there are instructions on the can, just follow them to the tee) I would switch over to paper towel as substrate for the time being. It will give the mites less crevices to lay eggs in as opposed to the Aspen, which you're going to have to toss anyway. If you have to wait on a can in the mail, I'd also provide a larger water bowl that he/she could soak in because it drowneds the living mites and gives him a bit of temporary relief.