iVillage: Why is FIV more commonly found in cats five years of age and older?
Dr. Zislin: It becomes clinical in cats that are middle age or older. But in most cases, I think cats become infected when they are much younger than that. Cats will become infected with the FIV virus, and often the virus in the cat will live without the cat showing signs for months to years. And then at some point down the line, the virus essentially takes over and destroys the cat's immune system. The reality is that very slowly the virus starts infecting more and more cells within the cat's system and destroys the immune system very slowly over a period of time. But in the early stages of the disease, many cats don't show any clinical signs. Many cats can live months to years without seemingly being sick.
iVillage: Can FIV be transferred in utero?
Dr. Zislin: That is an interesting question. For the most part that is not a common mode of transmission. Most of the time infected females do not pass the virus on to their kittens. The most common transmission is through bite wounds.
iVillage: What are the most common complications experienced by cats with FIV?
Dr. Zislin: The virus infects cells that fight infections for the cat (the white blood cells). And those white blood cells then become nonfunctional and decrease in numbers. So when the animal faces a viral infection, or a fungal or bacterial infection, it has less resistance to those disease agents.
iVillage: Meaning that any type of opportunistic infection is going to take over?
Dr. Zislin: Exactly. It is very similar to feline leukemia (FeLV).
iVillage: Why are multi-cat households more at risk?
Dr. Zislin: Just like anything else, if you've got one or two cats in the household, the chances for either one of those cats to become infected are extremely low. But as you add more and more cats to the household, you increase the chance of adding an infected cat. The close proximity the cats have in the household increases the chance for transmission to occur.
Unfortunately, what people tend to do is see a cat in the backyard that comes back repeatedly, feed the cat and then decide to bring that cat into their household, where they have other resident cats. They don't isolate or test the cat before integrating it into the household. And now, essentially, they've increased the chances for transmission because that outside cat may be infected with FIV or feline leukemia.
iVillage: If someone were to vaccinate a cat without having the blood test, could the vaccine activate the virus in a cat that is a carrier?
Dr. Zislin: No, the vaccine is safe in a cat that is infected with FIV or that is uninfected with FIV. We've done studies to be able to show that. But it really is good medicine to know the status of your cat before you start initiating a vaccine sequence. The vaccine will not fight off the virus; it is meant to prevent transmission of the virus. To be a preventative.
iVillage: What is a nonprogressor cat?
Dr. Zislin: Nonprogressor is a way of characterizing certain strains of FIV viruses. Many cats can live while being infected with FIV for years. And it's kind of interesting because in different parts of the world it's more common. For instance, in Australia, about a third of the cat population would test positive on the antibody test, and yet only a small percentage of cats actually get sick and die from FIV. Those strains of FIV that are infecting cats (and this is really true to Australia
iVillage: Could you tell me how the protective immune response works?
Dr. Zislin: The protective immune response for FIV is like any other viral infection. It's probably a combination of antibody production and the priming of certain types of white blood cells called T lymphocytes, which fight cells that are already infected with the virus. We know that cats that are infected with FIV will produce antibodies for the entire duration of the disease, and these are easily identifiable. That's the basis of the test that's used in a veterinary hospital to determine whether or not a cat is infected. And even though they have very high antibody levels, they don't get rid of the virus. So it's also important to stimulate the other portion of the immune system called cell-mediated immunity, the part that actually works with cells that are already infected with the virus. And we know from tests we've done in our own laboratory that the vaccine gets the cat to produce antibodies and activates the cell-mediated immunity portion of the immune system to make sure the cats don't get infected if they are challenged with the virus.
iVillage: Is the vaccine ever recommended for indoor-only cats in a vaccine protocol?
Dr. Zislin: I think good medical practice is that you select out those cats that are at high risk, and vaccinate them. If you have indoor cats but you also have an FIV-positive cat living with them, then those cats should be vaccinated. But if they are truly in a household with no FIV cats, then they are probably at low risk and people would probably elect not to vaccinate those cats.
iVillage: I wanted to ask a little more about the antibody test. After the vaccine, a cat will test positive. Is this common with other vaccines?
Dr. Zislin: It happens with every vaccine. Because precisely what we want to do when we vaccinate an animal is to simulate a natural infection as closely as possible. What we are trying to do is get the animal to very specifically produce antibodies that will fight off a natural challenge, so the response has to be as close as possible to a natural infection. If we got antibodies that were different than the type an animal would produce after being naturally infected, then they would not protect the cat against the challenge.
iVillage: With the current FIV diagnostic test, how reliable are the results?
Dr. Zislin: Quite reliable. It's a good screening test. Though if you get a positive test, it should be confirmed with another test called a Western Blot to rule out a false positive. So there's a backup test that's done at a commercial lab. It is routine in diagnostic testing to look for reproducible results from a couple different tests.
iVillage: If you have someone who has a couple of cats that are FIV-free and wants to bring home another cat, what can pet owners do to lessen the chance of exposure?
Dr. Zislin: Isolation. You'd bring the cat in, keep it in a separate area and make sure that when you are done handling that cat you wash your hands before you touch the other cats. You should probably do that for a couple of weeks. If the cat seems fine, then it should be checked out by a vet and checked for leukemia and FIV. If those tests are negative, then fully integrate that cat into the household.
You would also want to initiate a vaccine sequence, not knowing what the vaccine history is on that newly found cat. It takes about two weeks for any vaccine to illicit protective immunity in a cat. So that isolation should continue for a two-week period after the visit to the veterinary hospital.
iVillage: What is the most important thing to remember when dealing with vaccines?
Dr. Zislin: Feline vaccines have been around for about 30 years. Back in about 1970, the only thing we had to vaccinate cats for was rabies. Then the feline panleukopenia (FPV) vaccine came along. Prior to that it was a common thing to see cats with respiratory disease and kittens dying from panleukopenia, and vaccines have worked very well through mass immunization to minimize infectious disease in the cat population. But I think it's important for pet owners to get their information by talking to their vet. If their vet does not have the information, then they should challenge the vet to get the information.
FIV is a fatal disease. As far as we know, once a cat is infected, it is infected for life. And you can't even say that about FeLV, because some cats will actually become infected and get over the infection. So with FIV you've got one chance through vaccination to try to minimize the chance of that cat becoming permanently infected if it's at risk. Clearly we are not promoting this as a vaccine for every cat owner. But we are recommending it for cats that spend time outside. The consequences for not protecting a cat can be devastating.
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