Problems with current tests for FIV
by Brittany Roth, Calvin’s Paws Medical Care Coordinator and FIV/Felv Advisor
We hear it all the time. “I found a kitten and was going to keep it, but my vet just said she has FIV!” No, she probably doesn’t. Really.
There’s no question that all cats should be tested for FIV and FeLV, but the age at which they are tested is a source of some debate. The labs that make the tests say kittens can be tested at any age and the test will be accurate, but more and more rescues and vets are learning that this isn’t really the case. To understand why, let’s look at how the immune system works.
Antibodies are a part of the immune system that your body makes in response to infection. Once they have been produced in response to a specific pathogen (germ), the body can later recognize that pathogen and quickly attack it, preventing illness. There are several ways in which you can develop antibodies to a pathogen:
- You catch a disease and your body produces antibodies and fights the infection. Depending on the disease, you either fight it off completely or (as in the case of FIV) remain infected for life with your immune system keeping the infection suppressed.
- You are vaccinated against a disease and your body produces antibodies in response to the vaccine. You are then protected from future infection.
- Babies (or kittens) get antibodies from their mothers for a period after birth.
The most common test for FIV is an ELISA test (commonly called a SNAP test, although there are others on the market now) that is performed in house at your veterinarian’s office. This test looks for the antibodies to FIV in the cat’s blood. The problem is that this test cannot distinguish between the 3 ways of developing antibodies. So when a cat tests FIV+ on an ELISA test, it actually means one of 3 things:
- The cat is infected with FIV.
- The cat was once vaccinated against FIV.
- A kitten has antibodies to FIV from its mother (either because the mom was infected or vaccinated).
Are you beginning to see the problem here? Cats that come into rescues and shelters often come in as strays with no medical history. We have no way of knowing if a cat has been vaccinated for FIV; the FIV vaccine is not a “core” vaccine and is not usually recommended by the AAFP, but cats (especially ones that are indoor/outdoor) are still vaccinated.
How can you tell who actually has FIV?
We can’t. Adults that test FIV+ have the test repeated immediately to rule out test error, and then are retested again in a month. If they are still positive, then we have to consider them FIV+.
So why doesn’t my kitten have FIV again?
You have to keep in mind that FIV is very hard to transmit – it’s usually only spread through deep, intramuscular bites like the kind seen between unneutered males. Kittens younger than 6 months don’t really get in those types of fights. Stray kittens are also young enough that they probably haven’t had a previous owner that vaccinated them for FIV. So by process of elimination, the most likely reason that a kitten is testing FIV+ is because it still has antibodies to FIV from its mother. As the kitten gets older, those maternal antibodies fade and leave their system as the kitten’s own immune system develops. Once those maternal antibodies fade, the kitten will test negative for FIV. This typically happens by 6 months of age, although it is possible for it to take longer. For this reason, any kitten that tests positive for FIV should be retested at 6 months of age. Calvin’s Paws typically retests “FIV” kittens one month after the original test, because that is often long enough for the antibodies to clear, but any kitten that still tests positive is retested again at 6 months, and again at 1 year if needed. A diagnosis of FIV really cannot be made until the cat is a year old.
Well if this is true, why didn’t my vet tell me this?
FIV was only discovered around 30 years ago. Since then, numerous studies have shown that what we initially believed about FIV (that it’s very contagious and cats with FIV will live short, painful lives) is wrong. New research on FIV is coming out all the time, but some vets simply haven’t been well educated on the topic.
We have had countless kittens come into our program testing FIV+ over the years, and almost every single one of them has ended up being negative by 6 months of age. Here are just a few that we’ve had recently:
Snowden, Sheridan, and Sheldon: Found in a cemetery. Refused by other rescues because they were testing FIV+. All eventually tested negative and are in loving forever homes.
Catsby: Found as a stray and tested positive at finder’s vet. Tested negative within days of us taking him into the program.
Calvin’s Paws is a 501(c)(3) rescue. We work through a network of foster homes throughout the Triangle area to save homeless cats and dogs. We are a dedicated group of volunteers with common goals: rescuing animals (both positives and non-infected felines), finding the best fitting homes for each animal, and educating the public on animal health and responsible pet ownership.