Since E. coli is a normal inhabitant of the intestinal tract and the skin of the area under the tail extension of infection into the urinary tract is fairly common. As to whether this falls under the scope of your warranty might be influenced by when the problem was noticed in relation to receiving your puppy. You should contact the people who provided your puppy to you. I would be happy to answer any questions related to this problem or provide on opinion on warranty relevance if you need me to.