I had a similar situation with an abused friend. This poor fellow had his back legs tied togher so long they both rotted is sack and caused sores down the insides of his legs. He bit everything that even remotely resembled a hand. (he was a lab, about 8 months when I got him). It took me two years of 'a little bit at a time' of just talking, biting(I let him bit my protected hand over and over until)while I talked to him and told him it was okay to just let her all out. Eventually he got so tired of biting me that he would just give up. I kept treats on hand and made sure he was given one everytime he did something positive. I also taught him the basic commands of sit, stay, come, and fetch. This seemed over time to get his mind off of his 'problem'. It took two years to get him there and he never responded to anybody but me. Never bit anybody but I always felt he could. He lived to be 14 years old. So don't start if you don't have the patience to see it through but it can be done. Good Luck!!