I just got a call from my vet telling me that one of my cats tested positive for the heartworm antibody which means he has been exposed to heartworm. We are not in an area that sees a lot of heartworm infections. I took him in for his vaccines and rabies and mentioned inappropriate elimination and he had protein in his urine. We then got blood tests and this showed up. He is does go outdoors, but the vet said 11% of cats who test positive are indoor only. Am taking Lizzie and my other cat in today to get them tested. Lizzie tested negative when we got her, but I have not given her Sentinel routinely. Now I am freaking out!