A 3-year-old New Bedford girl was severely bitten by a pit bull last Friday as she walked with her grandmother on Brock Ave.   The child was bitten on the neck, arms and legs and transported to Rhode Island Hospital.   She was reportedly released later that same day.   According to New Bedford Animal Control director Manny Maciel, the dog has since been euthanized and the owner fined.  Eustaccia Biggs of Brock Avenue was cited for having an unlicensed dog and failing to restrain and vaccinate the dog.  A rabies test came back negative.