vet says its not ringworm or mange mites but..

Question
Have 2 guinea pigs we live trapped (these 2 escaped from Amish neighbors who basically were not as concerned about them as we were in the wild & they said we could keep after catching.) ..anyway...they are 2 males who are separated cuz the one is too much for the other dominion wise.  We noticed Max had a few areas on him w/missing hair, scabs , and a bloody spot, like a lesion.  Took to vet a month ago & vet did tests for ringworm and mites/mange and both came out negative .   Seemed to clear up ever slightly but now Im back to square one. I am going to make a vet apptment tomorrow /hope to get a diff one who is more knowledgeable about guinea pigs.  Max looks the worse, w/raw lesion looking spots and areas of missing hair.  Chino, our all white one has one spot w/missing hair and lesion. Do not see them even being bothered by the condition. Doesnt appear to cause them to itch but when touched they do appear sensitive. Its very ugly and Im concerned about other animals (cats and our dog) catching something from them so they are each in separate large cages (outdoors) w/a screened gazebo enclosure that allows shade and a breeze thru out the day.  ) Im afraid the ringworm test will come out negative again.  If its mange mites or lice wouldn't they be scratching incessantly?  I just don't know what to do...I read a couple websites that occassionally ringworm tests do come up  'false' negatives.  
Aside from visiting the vet again w/the 2 guinea pigs I thought I would ask you.  Thank you for your time.

Answer
Hi there

From the symptoms you describe, I am almost certain that your pigs are suffering from a fungal infection, as this always has lesions.

You can apply aloe vera gel to give the pigs more comfort. When you see the vet, ask them to prescribe Griseofulvin. Also, its good to treat fungal infections with parasitical medication also, Follicel is good for this.

I hope that helps

Andy