I have a hard time believing the DA in that county can't use another law for the purpose of charging the dog's owner. The owner is perfectly aware his dog is dangerous and even admits it. Since it's happened more than once why can't they charge him with assault with a deadly weapon?
Coming from a law enforcement standpoint, it's been my experience that the DAs and judges are often unwilling to think outside of the box. If they can't pigeon hole an offense they tend to sweep it under the rug. Unfortunately, it will probably take someone being killed by that dog before action is taken. Lawmakers would be much quicker to enact a vicious dog law if it were themselves or there loved ones being mauled.