I was out walking in rural Louisiana a couple of years ago and was surrounded by group of dogs lead by a pit bull. The other dogs circled me while the pit bull kept trying to get behind me biting at my calves. Fortunately a man saw what was happening, came running with a shovel and scattered the dogs. Other than having a heart rate greater than I anticipated from my walk, the pit bull just grazed one calf with his teeth.
When interviewed by sheriff's deputy that night the pit bull owner denied that the dog ever displayed any aggressive behavior and I must have provoked him (by walking down the road I guess).
I never walked by that place again and when I did walk in the area I always had a walking stick and bear spray.