I have a 1 1/2 year old staint bernard she has always been the frienliest dog ever. I have taken her to work with me in my taxi and never had and troubles with her. A few days ago I was on vacation and 3 times she went nuts and tried to bite my brother in law who loves pets and had just petted her 10 secounds earlier with out any negative rection. Then he said something very quietly and she turned into Cojoe and bite him and would have again if I had not have stopped her. Later she tried 2 more times. She is the most friendliest dog normally I asked my vet if it could be a bladder infection or some medical reason and she seemed not to care. I know people can have bladder infections or other medical problems that make them see things or have mood changes does anyone know what it could be or if dogs can have bladder infections that cause magor personaly changes or ?