HI. Well first I want to say, if you test a cat say today and it was exposed to feline leukemia yesterday it will be negative. Ok? Because it takes up to six months for the disease to show positive on a test. So a cat/kitten can be negative today and positive in 6 months. With that let me share a story, will try to make it short.
I took home Penny and her babies. Penny was tested negative. When her babies were 2-3 weeks old a single baby was pulled from the walling of a local business. Mom left her behind. So we tested her and I added her to my mom and babies. She was negative. I named her Stormy. (We made a decision to not test the kittens since mom was negative.) At 8-10 weeks old old a bunch were adopted, someone tested Stormy and it was positive. We called all owners and they brought them back to be tested, when the kittens were tested they showed positive. So Stormy and Penny were tested. Everyone was positive except one, but I told her to retest and am unsure if she ever did. However I received a photo of him recently and he looks great. Fingers crossed. Not testing those kittens was the biggest mistake ever. I've regretted it ever since.
So I think it came from Stormy.
I guess the bottom line is test all now, that way you know you did all you could. We have tested young kittens and they have come back positive so in my opinion it is well worth it.
The FIV I have limited knowledge about. It is not as common as feline leukemia and is transmitted through a bit, usually a deep bite. If a pet has been vx against it then they will test positive. I think the 6 month rule applies, but don't quote me.
Hope I helped some?
Last edited by doodlebug; 09-28-2010 at 12:36 AM.
Reason: Made a correction at OP's request.