I am so sorry to hear about your loss. Some of those kitty infectious diseases can be scary stuff. We had a run of feline leukemia here once with a foster cat. Luckily it was our only cat at the time and we were able to find it a home with another positive cat to live out its last years. We waited the appropriate amount of time before bringing anymore cats into our home and got them tested before doing so. It is a relief to know they are healthy and safe before it is too late. Now I always warn anyone bringing a cat into their home to have any and all health tests possible done before letting it come into their home, especially if they already have cats. FPV is from what I understand a lot harder to test for than FeLV, so that really is devastating. Again, I am sorry to hear about your baby.
