Oh wow! How terrible that the Belle was suffering because of that her owner. I am so glad that you were available to help her. From what I understand, maggots feed on dead flesh - they used to be used to clean wounds - they would eat away all of the dead flesh so that the live flesh could heal. In fact some doctors are using sterile maggots and leaches for that very purpose in certain types of wounds. Here is an article - I found a utube video of someone being treated with maggots, even though it was working miracles on the wound, I will spare you - it was really gross....
USATODAY.com - Maggots and leeches: Good medicine