Don't let the vet give a shot of Ivermectin. It's a pesticide. This is controvercial among vets who get hassled by Web-advised patients, but Ivermectin is very hard on the kidneys. Let him give you Ivermectin, if he has to give you some, to externally treat his skin and cage.
Read up on mites and mite control:
http://www.anapsid.org/mites.html
Know your enemy. You might alienate your vet, and if that happens, it must be so. Be apologetic.
Roger

