A veterinarian can diagnose this mite infestation by performing skin scrapings of affected areas and viewing them under the microscope. Successful treatment consists of one to four injections of a specific antiparasitic drug at approximately two week intervals. In the meantime, if wood shavings are used as bedding or litter, it should be replaced with paper toweling to make your pet more comfortable.
I have to disagree with some of that information.
The skin scraping is painful for guinea pigs and often returns a false negative. Unless the vet takes skin from a precise place where the mites are, they will not show, even if there are mites on the cavy. The treatment for the mites is perfectly safe, and if they are suspected can be treated safely even if they are not on the cavy.
About successful treatment being 1 to 4 injections, 1 isn't enough to kill the parasite, at least two is needed in minor infections, 3 or 4 in more severe. The injections should be anywhere from 7 to 10 days apart.
just my 2 cents input