Those little brown bugs would be rat lice. You will need to see a vet and he will prescribe you some Ivermectin with a correct doseage based on weight. Or, you can do like a lot of rat owners are now doing and get some Frontline or Advantage (NOT Advantix) and put ONE DROP of the stuff on the back of the neck/shoulder area. I use this with my rats and have not had a problem with mites or lice ever since. Typically these bugs get in on bedding bought from Pet stores. Good luck !
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-Melina