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Dear Christopher Cat

Our veterinarian vaccinates our indoor-outdoor cats with the distemper combo, rabies and feline leukemia vaccines. Should our cats be immunized against FIV also?

Christopher Responds

Most cats would answer “no,” but I’ll give you some background so you can decide for yourselves.

FIV, feline immunodeficiency virus, suppresses the cat’s immune system and is incurable.   The virus is transmitted from cat to cat through bite wounds, so a vaccine would seem to make sense for outdoor cats.

However, the FIV vaccine has two limitations. First, it is only 82 percent effective at preventing one of the two types of FIV found in the United States, and it is ineffective against the other.

Even more serious, the FIV vaccine interferes with subsequent FIV testing. Let me explain why this is important.

After vaccination, we develop antibodies against the feline immunodeficiency virus. FIV tests detect antibodies, but none of the commercially available tests can differentiate vaccine-induced antibodies from antibodies associated with the disease itself.

So if one of your vaccinated cats develops problems suggestive of FIV, your veterinarian can’t use an FIV test to determine whether your cat actually has the disease.

Worse yet, if one of your vaccinated cats strays from home and is found, his FIV test will be positive. The shelter won’t know whether he is infected with FIV or merely vaccinated – or both – and may elect to euthanize him.

If you decide to vaccinate your cats for FIV, be sure they test negative before vaccination and that they are identified with a tag, microchip and perhaps even a tattoo so they will be returned to you if they stray.

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