The dog has an advanced sarna, the skin disease caused by parasites that took months to develop to present stage. Who on earth leaves an animal like this, without treating it? These people have no heart.
It is a young dog, he is around one year old. Fortunately he does not have another health problems. We had dogs in a similar state before, nearly naked without fur and it is treatable. Takes long time but one day he will be a beautiful dog and will find a new home.