The balding patches are not fleas, this is a sign and or symptom of mites, make an appointment with a veterinarian that deals with exotic pet. The vet will do a skin scrapping to confirm that they are mite and he will treat them with ivometrin. If you do not take care of this your piggy will start to scratch these bald spot making a very large scab, the piggy will continue to scratch an get a secondary infection that will in the end, end his life.