<<<I have a question for Dr. Susan, actually, it's a couple of questions.
As you know from my posts, Timmy has tested negative. That's great
news, and I hate to look a gift test in the tube, but, I know that it's
possible that the FeLV is sequestered in his bone marrow and not able to
be detected by the ELISA. I had thought that the only way to tell for
sure if he has indeed shucked the virus and is truly negative, was to do
a bone marrow test. Lisa posted that latent FeLV can also be determined
with a PCR test (Polymerase Chain Reaction) using a blood sample. Is
this test reliable for this purpose?
Also, if a cat was positive and later tests negative, does that mean he
will forever be immune to the disease? If that's the case, it wouldn't
be necessary to vaccinate against FeLV, is that correct?
Thank you so much for getting these questions to Dr. Susan, and thank
Dr. Susan for her gracious help with our babies. >>>
PCR tests for FeLV on blood are not widely recommended; I don't use PCR
tests for FeLV or FIV. There can be significant quality control issues with
these tests and they have not been well evaluated. PCR on blood would not be
able to detect a truly latently infected cat. Latently infected cats are
negative on all tests because the virus has integrated itself into the cat's
own DNA and cannot be detected. Most cats will eventually clear these cells
from their body and become truly negative, but a small number will harbour
the viral DNA and could re-activate the latent infection in the future.
Cats that have cleared FeLV infection will have antibodies for some time,
but we don't know how long they are protected. In general, resistance to
FeLV naturally increases with age anyway. If the cat is still at risk of
FeLV infection, it should be vaccinated as any other cat at risk would be.
Dr. Susan
Chapter Author, A Home Veterinary Guide, in:
The CFA Complete Cat Book
http://www.cfainc.org/catalog/books.html#completecatbook
Feline Reproduction Manual:
http://catvet.homestead.com/ReproCD.html
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Susan Little, DVM
Diplomate ABVP (Feline)
Bytown Cat Hospital
Ottawa, Canada
http://catvet.homestead.com
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