well, I actually use frontline, they said though that it could have been up to a year ago that he was bit. we took him camping with us and did find the large grey tick, which is what i think they are calling a deer tick.The vet said that all of his symptoms could be explained that way, just unusual presentation of them, usually its the front leg that has the lameness, and theres usually los of appetite and vomiting, he showed no signs of either, and they also said, that it would and can present this quickly. they are still waiting on an ultrasound, just to investigate the masses better, and so far the vet is just doing every thing they can to make him comfy, we visited him today, and they said he was up walking more. I just hope that thats all it is, we are getting tither(sp) for our female and pups that are here, they said its not transferable but i would rather be safe than sorry, I figure if none of the others test positive than we will be ok, but if any test positive than all twelve will be coming back for evaluation and treatment. I am still keeping my fingers crossed, my poor doggie is all alone up there!..he cried when we left..made my heart break. let me tell ya, i hope that he can come home soon, hes been here all my kids life, and they are really making it twice as hard!...