Probably, she suffered from rabies.

 It sounds like this puppy could have some kind of disease form an infection caused by the open wound. You are doing a good job at cleaning it every day, and God bless you for taking this animal in, but I would suggest phoning a vet and explaining the situation to them. They might be able to help you over the phone, or as this puppy is a stray, be able to cut down on medical costs for it at this stage.
 
The puppy could also be allergic to fura-zone - they also tend to get skin allergies.
 
What worries me the most is that you say the meat is fully exposed. This needs to be closed up (stitches) as soon as possible, because until that wound is not healed, the more risk of infection is involved and could lead to something worse. 
 
It is better to prevent further illness to just get advice from a professional in this regard, I do not mean to scare you, but the puppy's life might be at risk if the exposed flesh and spreading infection is not treated as soon as possible.
 
Hope this helps, once again, you are a hero for taking this puppy in. Good luck to you!

 It sounds like an infection. You should take it to the vet for antibiotics.