What is the correct solution?

Before I ask this question please understand that I did try to do my best for this situation. My brother has a german shepherd/boxer mix dog who's is probably 2 or 3 yrs old. He has left him in the care of my father who is in his mid 70's. My brother does buy the dog food , but my dad is the one who cares for him. My dad is not getting around as easily as he used too and some days the poor dog doesn't eat unless one of my nephews comes and visits since my dad lives alone, I recently went for a visit and i was disgusted at the condition of the poor dog, he's skinny and has some sort of skin condition . He is chained up and the chain isn't very long so he has to step and sleep in his own feces. I told my brother to take the dog to the animal shelter because my dad can not take care of him. My brother refused saying that the dog was like a guard dog for my dad and alerted him when someone was around. I called the animal shelter and told them to come for the dog and they didn't take him because my brother refused. I don't know what to do, I live 18hrs away and only visit for a year. I know my brother knows better than that since he has a min pin who is very healthy and has all the medical care he needs. What can I do to help this poor dog?