Okay this actually entails a really long explanation so I am going to try to come up with something short) and get back to you. I can say that sadly in Washington State the law considers pets a "good" or "personal property" hence their sale will be governed by Article II of the Uniform Commercial Code. What I would ask so that I could give you a better idea of what you are dealing with is this: Did your puppy come with any paperwork at the time of purchase? If so what does it say? What gaurantees were made to you in any way before the actual exchange of money for puppy? Did you have any express or written warranty? When did you discover the illness/what is the illness/did you have the puppy examined by a vet directlyn after purchase,etc?
I would like to give you any advice I could, but I should warn you I am only a law student and not an attorney, but I have very few credits to go until I am
and currently am doing a clerkship in commerical litigation so I am fairly familiar with sales transactions.